Dell H4X6X / 770-BBIN B6 ReadyRails II 2U Sliding Rail Kit — for PowerEdge R720, R730, R740, R750 and Related 2U Chassis
Warranty: Lifetime
Sliding ReadyRails II (B6) — the 2U service-extend kit, not the static / VersaRails / 1U kit
Dell H4X6X / 770-BBIN — ReadyRails II 2U sliding rails for PowerEdge and related 2U chassis
Dell Part Number: H4X6X
Dell Order Code / MPN aliases: 770-BBIN, 0384R, 0H4X6X, XV104, 0XV104, 0PWN3, 61KCY, MMK10 (and related 0-prefixed stickers)
Description: B6 ReadyRails II sliding rail kit for 2U systems — tool-less mount in 4-post square-hole and unthreaded round-hole racks; tooled mount in threaded-hole racks
This is the sliding rail kit — the one that lets you fully extend a 2U chassis out of the rack for service. Most sliding B6 kits support an optional cable management arm (CMA) so you can pull the system without disconnecting rear cables. The CMA is not in this box; the kit ships with two rail assemblies and two hook-and-loop straps for basic rear cable routing.
Dell labels this mounting interface ReadyRails II and the rail identifier B6 (stamped on the rails). Older docs and BOMs may also show order codes like 770-BBIN or manufacturing stickers like 0H4X6X / 0PWN3. Same kit family.
Which One Do I Need?
| Going into | You need |
|---|---|
| 2U PowerEdge with B6 ReadyRails II chassis mounts (R520/R530/R540 family, R720/R730/R740/R750 family, R820/R830, and related — see specs) | Sliding ReadyRails II (B6) — this product |
| Same 2U chassis, but you only need fixed mount (no in-rack service slide-out) | B4 ReadyRails static rails — not this kit |
| 1U PowerEdge (R620/R630/R640 family and similar) | A7 ReadyRails II 1U sliding rails — not this kit |
| 2-post relay rack, or a chassis that requires VersaRails / RapidRails | Different mounting interface — not this kit (B6 sliding does not support 2-post) |
| You need organized rear cables while the system is fully extended | This kit plus the matching optional 2U CMA (sold separately) |
Sliding vs static is the first fork. Sliding extends for service and can take a CMA. Static stays put, fits more rack types (including many 2-post installs), and never takes a CMA.
A 1U chassis does not take this kit. ReadyRails II 1U systems use a different rail identifier (commonly A7). Ordering by “ReadyRails” alone is how wrong-U kits get bought.
Technical Specifications
| Specification | Value |
|---|---|
| Dell Part Number | H4X6X |
| Common Order / Alias Numbers | 770-BBIN, 0384R, 0H4X6X, XV104 / 0XV104, 0PWN3, 61KCY, MMK10 / 0MMK10 (reseller cross-refs also cite 5Y77W, 770-BBKW, 331-4436) |
| Rail Identifier | B6 |
| Mounting Interface | ReadyRails II |
| Rail Type | Sliding (drop-in inner slides; full extension for service) |
| Form Factor / U Height | 2U |
| Kit Contents | Two B6 ReadyRails II sliding rail assemblies · Two hook-and-loop straps · CMA not included |
| 4-Post Square-Hole Racks | Tool-less |
| 4-Post Unthreaded Round-Hole Racks | Tool-less (≈6 mm offset from post vs square-hole flush mount) |
| 4-Post Threaded-Hole Racks | Tooled — minor conversion; user-supplied screws (#10-32, #12-24, M5, or M6); screw head diameter must be ≤10 mm; screws not in kit |
| 2-Post Racks | Not supported on B6 sliding |
| Rail Adjustability (typical B6 group) | Square ≈631–868 mm · Round ≈617–861 mm · Threaded ≈631–883 mm (R820/R830 group uses a slightly deeper min range — verify if rack is shallow) |
| Rail Depth | ≈714 mm without CMA brackets · ≈845 mm with CMA (per Dell rail sizing matrix) |
| CMA Support | Optional CMA mounts left or right without tools — sold separately |
| Primary Compatible Chassis (Dell matrix / Dell shop) | PowerEdge R520, R530, R540, R540xd · R720, R720xd, R730, R730xd · R740, R740xd, R7415, R7425 · R7515 · R820, R830 · Precision R7910 / 7920 Rack · PowerVault NX3200 · Compellent SC8000 · related PowerVault/DR nodes commonly listed with 770-BBIN |
| Also commonly listed (verify on current Dell matrix for your exact SKU) | PowerEdge R750, R7525 · R550 / R550xs (reseller lists; confirm rail identifier B6 on your chassis) |
| Static Counterpart | B4 ReadyRails static rails |
| Standards | Designed for EIA-310 19-inch 4-post racks |
| Warranty | Lifetime, backed by Resilient Tec |
| Condition | New |
Note on Sliding vs Static, ReadyRails II vs VersaRails, and 2U vs 1U
Buyers searching “Dell rails” hit four different products that look alike in a photo: sliding vs static, ReadyRails II vs older ReadyRails / VersaRails / RapidRails, 2U vs 1U, and rails-only vs rails+CMA.
Sliding (this kit) fully extends the chassis for service and can take an optional CMA. Static (B4) does not slide for service, does not take a CMA, and covers more rack types — including many 2-post installs. If you never pull the server out on rails, static may be the better buy; if you do, this is the kit.
ReadyRails II is tool-less in square and unthreaded round 4-post racks, with native tooled support for threaded posts after a pin/latch conversion. VersaRails is a different, typically tooled interface (and Dell does not recommend VersaRails in threaded-hole racks). RapidRails is square-hole tool-less only. Do not substitute by name alone — match the rail identifier on the chassis docs (B6 for this product).
2U vs 1U: this kit is 2U / B6. A 1U ReadyRails II sliding kit is a different identifier (commonly A7) and will not correctly support a 2U chassis. Count the U height on the bezel and the rail identifier stamped on existing rails before you reorder.
Good to Know
- CMA is not in the box. Dell’s B6 sliding installation guide lists two rail assemblies and two hook-and-loop straps. If you need continuous power/data while the system is fully extended, order the matching optional 2U CMA separately.
- Threaded racks need your screws. For threaded-hole 4-post racks you remove the tool-less pins/latches and use eight user-supplied screws (#10-32, #12-24, M5, or M6) with head diameter ≤10 mm. Screws are not included.
- 2-post racks are a hard no for B6 sliding. If you are in a relay / telco 2-post rack, look at the static B4 path (or another Dell-supported 2-post option) instead of forcing this kit.
- Round-hole racks sit slightly proud. ReadyRails II in unthreaded round holes offsets about 6 mm from the post vs flush square-hole mount — that also shifts the bezel slightly. Plan door clearance accordingly.
- Shallow racks + CMA = depth math. With CMA attached, rail depth is about 845 mm. If you do not need the CMA, removing the outer CMA brackets shortens the rail footprint (Dell cites ≈714 mm without those brackets) and can clear rear PDUs or a tight rear door.
- Wrong U height is the most common wrong order. H4X6X is 2U. 1U kits, 4U kits, and older RapidRails/VersaRails kits will not substitute cleanly just because they say “Dell rails.”
- R820/R830 use the same B6 identifier but Dell’s sizing matrix shows a slightly deeper minimum adjustability range than the R720/R740 group. If your rack is unusually shallow, check post-to-post distance against the matrix before you commit.
- Confirm the rail identifier in your server’s rack installation section if you are on a less common SKU (storage nodes, Precision rack workstations, later 15th-gen 2U). When the chassis docs say B6 ReadyRails II sliding, this is the family.
Quick Checklist — Is This the Right Kit?
You are racking a 2U Dell system whose docs call for B6 ReadyRails II sliding rails (PowerEdge R520/R530/R540, R720/R730/R740/R750-class, R820/R830, Precision R7910/7920 Rack, NX3200, SC8000, or another B6-listed chassis). Your rack is a 4-post EIA-310 cabinet with square or unthreaded round holes (or threaded holes where you will supply the correct screws). You want to fully extend the chassis for service. You understand the optional CMA is separate.
Availability
In stock at Resilient Tec · Additional units ship on a 7–10 day lead time.
Outfitting a row of 2U PowerEdges? Tell us how many chassis and whether you need CMAs and we will quote rails and arms together. Request a quote →
Warranty: lifetime, backed by Resilient Tec — not a manufacturer term. When a kit fails you reach a named seller in the US, not a ticket queue.
You Might Also Need
- Optional 2U cable management arm (CMA) matched to B6 sliding rails — keeps power/data connected while the chassis is fully extended (sold separately; confirm the CMA SKU for your generation)
- B4 ReadyRails static 2U rails — when you want fixed mount, 2-post flexibility, or no slide-out service
- A7 ReadyRails II 1U sliding rails — only if the chassis is actually 1U, not 2U
- User-supplied rack screws for threaded-hole posts (#10-32, #12-24, M5, or M6, head ≤10 mm)
- Request a quote — multi-kit / multi-rack builds, mixed static + sliding rows, or “I have a chassis tag photo, which rails?”
- Product guides — structured rack and cabling notes as we publish them
Related Guides
Dell Enterprise Systems Rail Sizing and Rack Compatibility Matrix (Dell engineering PDF) — rail identifier, adjustability ranges, and CMA depth by platform
Dell B6 ReadyRails II sliding rails installation guide — tool-less square/round install, threaded conversion, and kit contents
Not sure which rail kit matches your chassis tag? Send the service tag or a photo of the existing rail stamp (A7 / B6 / B4, etc.) and we will point you at the correct kit rather than guess.
Sliding ReadyRails II (B6) — the 2U service-extend kit, not the static / VersaRails / 1U kit
Dell H4X6X / 770-BBIN — ReadyRails II 2U sliding rails for PowerEdge and related 2U chassis
Dell Part Number: H4X6X
Dell Order Code / MPN aliases: 770-BBIN, 0384R, 0H4X6X, XV104, 0XV104, 0PWN3, 61KCY, MMK10 (and related 0-prefixed stickers)
Description: B6 ReadyRails II sliding rail kit for 2U systems — tool-less mount in 4-post square-hole and unthreaded round-hole racks; tooled mount in threaded-hole racks
This is the sliding rail kit — the one that lets you fully extend a 2U chassis out of the rack for service. Most sliding B6 kits support an optional cable management arm (CMA) so you can pull the system without disconnecting rear cables. The CMA is not in this box; the kit ships with two rail assemblies and two hook-and-loop straps for basic rear cable routing.
Dell labels this mounting interface ReadyRails II and the rail identifier B6 (stamped on the rails). Older docs and BOMs may also show order codes like 770-BBIN or manufacturing stickers like 0H4X6X / 0PWN3. Same kit family.
Which One Do I Need?
| Going into | You need |
|---|---|
| 2U PowerEdge with B6 ReadyRails II chassis mounts (R520/R530/R540 family, R720/R730/R740/R750 family, R820/R830, and related — see specs) | Sliding ReadyRails II (B6) — this product |
| Same 2U chassis, but you only need fixed mount (no in-rack service slide-out) | B4 ReadyRails static rails — not this kit |
| 1U PowerEdge (R620/R630/R640 family and similar) | A7 ReadyRails II 1U sliding rails — not this kit |
| 2-post relay rack, or a chassis that requires VersaRails / RapidRails | Different mounting interface — not this kit (B6 sliding does not support 2-post) |
| You need organized rear cables while the system is fully extended | This kit plus the matching optional 2U CMA (sold separately) |
Sliding vs static is the first fork. Sliding extends for service and can take a CMA. Static stays put, fits more rack types (including many 2-post installs), and never takes a CMA.
A 1U chassis does not take this kit. ReadyRails II 1U systems use a different rail identifier (commonly A7). Ordering by “ReadyRails” alone is how wrong-U kits get bought.
Technical Specifications
| Specification | Value |
|---|---|
| Dell Part Number | H4X6X |
| Common Order / Alias Numbers | 770-BBIN, 0384R, 0H4X6X, XV104 / 0XV104, 0PWN3, 61KCY, MMK10 / 0MMK10 (reseller cross-refs also cite 5Y77W, 770-BBKW, 331-4436) |
| Rail Identifier | B6 |
| Mounting Interface | ReadyRails II |
| Rail Type | Sliding (drop-in inner slides; full extension for service) |
| Form Factor / U Height | 2U |
| Kit Contents | Two B6 ReadyRails II sliding rail assemblies · Two hook-and-loop straps · CMA not included |
| 4-Post Square-Hole Racks | Tool-less |
| 4-Post Unthreaded Round-Hole Racks | Tool-less (≈6 mm offset from post vs square-hole flush mount) |
| 4-Post Threaded-Hole Racks | Tooled — minor conversion; user-supplied screws (#10-32, #12-24, M5, or M6); screw head diameter must be ≤10 mm; screws not in kit |
| 2-Post Racks | Not supported on B6 sliding |
| Rail Adjustability (typical B6 group) | Square ≈631–868 mm · Round ≈617–861 mm · Threaded ≈631–883 mm (R820/R830 group uses a slightly deeper min range — verify if rack is shallow) |
| Rail Depth | ≈714 mm without CMA brackets · ≈845 mm with CMA (per Dell rail sizing matrix) |
| CMA Support | Optional CMA mounts left or right without tools — sold separately |
| Primary Compatible Chassis (Dell matrix / Dell shop) | PowerEdge R520, R530, R540, R540xd · R720, R720xd, R730, R730xd · R740, R740xd, R7415, R7425 · R7515 · R820, R830 · Precision R7910 / 7920 Rack · PowerVault NX3200 · Compellent SC8000 · related PowerVault/DR nodes commonly listed with 770-BBIN |
| Also commonly listed (verify on current Dell matrix for your exact SKU) | PowerEdge R750, R7525 · R550 / R550xs (reseller lists; confirm rail identifier B6 on your chassis) |
| Static Counterpart | B4 ReadyRails static rails |
| Standards | Designed for EIA-310 19-inch 4-post racks |
| Warranty | Lifetime, backed by Resilient Tec |
| Condition | New |
Note on Sliding vs Static, ReadyRails II vs VersaRails, and 2U vs 1U
Buyers searching “Dell rails” hit four different products that look alike in a photo: sliding vs static, ReadyRails II vs older ReadyRails / VersaRails / RapidRails, 2U vs 1U, and rails-only vs rails+CMA.
Sliding (this kit) fully extends the chassis for service and can take an optional CMA. Static (B4) does not slide for service, does not take a CMA, and covers more rack types — including many 2-post installs. If you never pull the server out on rails, static may be the better buy; if you do, this is the kit.
ReadyRails II is tool-less in square and unthreaded round 4-post racks, with native tooled support for threaded posts after a pin/latch conversion. VersaRails is a different, typically tooled interface (and Dell does not recommend VersaRails in threaded-hole racks). RapidRails is square-hole tool-less only. Do not substitute by name alone — match the rail identifier on the chassis docs (B6 for this product).
2U vs 1U: this kit is 2U / B6. A 1U ReadyRails II sliding kit is a different identifier (commonly A7) and will not correctly support a 2U chassis. Count the U height on the bezel and the rail identifier stamped on existing rails before you reorder.
Good to Know
- CMA is not in the box. Dell’s B6 sliding installation guide lists two rail assemblies and two hook-and-loop straps. If you need continuous power/data while the system is fully extended, order the matching optional 2U CMA separately.
- Threaded racks need your screws. For threaded-hole 4-post racks you remove the tool-less pins/latches and use eight user-supplied screws (#10-32, #12-24, M5, or M6) with head diameter ≤10 mm. Screws are not included.
- 2-post racks are a hard no for B6 sliding. If you are in a relay / telco 2-post rack, look at the static B4 path (or another Dell-supported 2-post option) instead of forcing this kit.
- Round-hole racks sit slightly proud. ReadyRails II in unthreaded round holes offsets about 6 mm from the post vs flush square-hole mount — that also shifts the bezel slightly. Plan door clearance accordingly.
- Shallow racks + CMA = depth math. With CMA attached, rail depth is about 845 mm. If you do not need the CMA, removing the outer CMA brackets shortens the rail footprint (Dell cites ≈714 mm without those brackets) and can clear rear PDUs or a tight rear door.
- Wrong U height is the most common wrong order. H4X6X is 2U. 1U kits, 4U kits, and older RapidRails/VersaRails kits will not substitute cleanly just because they say “Dell rails.”
- R820/R830 use the same B6 identifier but Dell’s sizing matrix shows a slightly deeper minimum adjustability range than the R720/R740 group. If your rack is unusually shallow, check post-to-post distance against the matrix before you commit.
- Confirm the rail identifier in your server’s rack installation section if you are on a less common SKU (storage nodes, Precision rack workstations, later 15th-gen 2U). When the chassis docs say B6 ReadyRails II sliding, this is the family.
Quick Checklist — Is This the Right Kit?
You are racking a 2U Dell system whose docs call for B6 ReadyRails II sliding rails (PowerEdge R520/R530/R540, R720/R730/R740/R750-class, R820/R830, Precision R7910/7920 Rack, NX3200, SC8000, or another B6-listed chassis). Your rack is a 4-post EIA-310 cabinet with square or unthreaded round holes (or threaded holes where you will supply the correct screws). You want to fully extend the chassis for service. You understand the optional CMA is separate.
Availability
In stock at Resilient Tec · Additional units ship on a 7–10 day lead time.
Outfitting a row of 2U PowerEdges? Tell us how many chassis and whether you need CMAs and we will quote rails and arms together. Request a quote →
Warranty: lifetime, backed by Resilient Tec — not a manufacturer term. When a kit fails you reach a named seller in the US, not a ticket queue.
You Might Also Need
- Optional 2U cable management arm (CMA) matched to B6 sliding rails — keeps power/data connected while the chassis is fully extended (sold separately; confirm the CMA SKU for your generation)
- B4 ReadyRails static 2U rails — when you want fixed mount, 2-post flexibility, or no slide-out service
- A7 ReadyRails II 1U sliding rails — only if the chassis is actually 1U, not 2U
- User-supplied rack screws for threaded-hole posts (#10-32, #12-24, M5, or M6, head ≤10 mm)
- Request a quote — multi-kit / multi-rack builds, mixed static + sliding rows, or “I have a chassis tag photo, which rails?”
- Product guides — structured rack and cabling notes as we publish them
Related Guides
Dell Enterprise Systems Rail Sizing and Rack Compatibility Matrix (Dell engineering PDF) — rail identifier, adjustability ranges, and CMA depth by platform
Dell B6 ReadyRails II sliding rails installation guide — tool-less square/round install, threaded conversion, and kit contents
Not sure which rail kit matches your chassis tag? Send the service tag or a photo of the existing rail stamp (A7 / B6 / B4, etc.) and we will point you at the correct kit rather than guess.