10-52 teeth. 520% of range. On a standard HG freehub.

That last part is the news. Every other Eagle Transmission cassette requires an XD driver body. This one doesn't — SRAM integrated the 10-tooth cog into the lockring, which means a full 10-52 range fits on the same splined freehub that's been on mountain bikes for two decades.

Cog sizes: 10, 12, 14, 16, 18, 21, 24, 28, 32, 38, 44, 52.

Why the HG driver matters

If you've priced a Transmission upgrade before, you've run into this: the cassette needs an XD driver body, and if your wheels don't have one, you're buying a driver body — or a whole rear wheel — on top of the drivetrain.

The XS-1270 removes that line item. It mounts to a standard splined 8, 9, or 10-speed HG driver. On an 11-speed HG driver, it needs a 1.85mm spacer and nothing else.

It's also approved for aluminum driver bodies, not just steel, and rated for both MTB and E-MTB use. That's not a given on a cassette with a 10-tooth cog — the small cogs concentrate a lot of torque into a few splines, and plenty of cassettes are steel-driver-only for that reason.

Practical result: on a lot of bikes this is a drivetrain upgrade that doesn't turn into a wheel upgrade.

You need a full Transmission setup

This cassette is one part of an integrated system, and it will not work outside it.

• Eagle Transmission (T-Type) rear derailleur. Transmission derailleurs and cassettes are designed to physically reference each other. A standard Eagle or Eagle AXS derailleur will not shift this correctly.
• A UDH frame. Transmission derailleurs mount directly through a UDH-standard dropout with no hanger. If your frame uses any other hanger pattern, Transmission won't fit it.
• A 55mm chainline crank. This cassette's gear positions are built around a 55mm chainline, which means a T-Type or MTB Wide crankset.
• A T-Type chain. Not Eagle 12-speed, not Flattop, not Shimano. T-Type.

1x only. There's no front derailleur configuration for Transmission.

What Transmission actually does differently

The reason to run this system isn't the range — plenty of drivetrains have wide range. It's what happens when you shift under load.

Because the derailleur bolts directly to the frame instead of hanging off a bendable hanger, and because the cassette's tooth profiles are cut to hand the chain off at specific points in the rotation, Transmission will complete a shift with full power going through the pedals. Standing, mid-climb, out of a corner. The system is designed for the shift you'd normally back off for.

Setup is the other half. There are no limit screws and no B-gap adjustment. A clearly marked Setup Cog on the cassette gives the derailleur its reference point, you follow the printed procedure once, and it's done. No hanger alignment, ever, because there's no hanger.

Replaceable cluster

Gears 8 through 12 — the 28, 32, 38, 44, and 52 — come off as a replaceable cluster rather than being pinned permanently into the stack.

On a 1x mountain drivetrain those are the cogs doing the heavy work, and they're the ones that wear out first. Being able to replace that section instead of the entire cassette is a meaningful reduction in what this drivetrain costs to keep running over a few seasons.

Gear steps

The steps are wider than a road cassette, and deliberately so. Mountain riding doesn't ask you to fine-tune cadence — it asks for a gear that works for the next fifty feet of trail, right now.

Two-tooth steps through the fast end keep the top of the range usable on fire roads and flat transfers. The bottom opens up into the 38, 44, and 52 that turn a steep, loose, technical climb from a hike-a-bike into a ride.

520% of range from a single ring. On a 32T chainring, that's roughly 3.2:1 at the top down to 0.62:1 at the bottom.

Built to last

Black nickel chrome plating adds surface hardness and runs quieter under the chain. Full X-SYNC tooth design across the whole cassette handles both inboard and outboard shifts under load — the shifting profiles are cut into every cog, not just the ramps between a few of them.

What you'll still need

• An Eagle Transmission (T-Type) rear derailleur and a UDH frame to mount it to
• A 55mm chainline crankset — T-Type or MTB Wide
• A T-Type chain
• A 1.85mm spacer if you're mounting to an 11-speed HG driver
• A cassette lockring tool

Fitment

• Driver body: Splined HG 8, 9, or 10-speed. Fits an 11-speed HG driver with a 1.85mm spacer. Not XD or XDR.
• Driver material: Approved for both steel and aluminum
• Speeds: 12
• Drivetrain: 1x only
• Chainline: 55mm
• Rear derailleur: Eagle Transmission (T-Type) only
• Chain: T-Type only
• Applications: MTB and E-MTB approved

Specifications

• Model: CS-XS-1270-A1
• Part number: 00.2418.141.002
• Gearing: 10-52T
• Cog sizes: 10, 12, 14, 16, 18, 21, 24, 28, 32, 38, 44, 52
• Speeds: 12
• Total range: 520%
• Weight: 565g
• Finish: Black nickel chrome
• Driver body interface: Splined 8, 9, 10
• Drivetrain configuration: 1x
• Chain technology: T-Type
• Replaceable cluster: Gears 8-12

Installation

Find the marked Setup Cog before you start — that's the reference the derailleur sets itself against, and the Transmission setup procedure depends on it. Follow SRAM's printed sequence rather than improvising; there are no limit screws to fall back on if you skip a step.

Torque the lockring to spec with a torque wrench. A little anti-seize on the driver splines makes removal much easier a year from now.

Replace the chain at the same time if the old one is worn. A worn chain on a new cassette will chew the new cogs quickly, and you'll be buying both again.

Full documentation is available in SRAM's service hub for this model.

OE product information

Not intended for retail sale. This is original-equipment product supplied for dealer service, warranty replacement, and complete-bike build applications.

OE product is the same component that ships on complete bikes — identical specification, identical performance. What differs is how it's supplied:

• Plain bulk or poly packaging rather than a retail box
• No printed manuals or quick-start guides — all documentation is available free from SRAM's service hub, linked above
• No retail hang tags or display materials
• Small-parts and hardware content may differ from the retail pack
• Components may show minor handling marks from bulk packing

Warranty. SRAM's consumer warranty program does not apply to original-equipment components. Warranty and defect claims on this item are administered by State Bicycle Co. Contact our support team with your order number. Wear is not a defect — cassettes are a consumable.

Original equipment service item. Supplied in OE packaging for dealer service, warranty replacement, and complete-bike build applications; not a retail-packaged consumer product and not intended for retail sale. SRAM consumer warranty does not apply to original-equipment components — warranty administration on this item is provided by State Bicycle Co. Requires an Eagle Transmission (T-Type) rear derailleur, a UDH-compatible frame, a 55mm chainline crankset, and a T-Type chain. Not compatible with standard Eagle drivetrains, XD, or XDR driver bodies. SRAM, Eagle, Transmission, T-Type, AXS, XS, X-SYNC, and UDH are trademarks of SRAM LLC. State Bicycle Co. is not affiliated with or endorsed by SRAM LLC. Specifications subject to change without notice.