X4 Unibody Cog Set 4 cogs 11/13/17/21t for Brompton 2/6 speed wheelset (MiniMODs) 2S->4S or 6S->12S

Brompton X4 Unibody Cog Set (11/13/17/21T) Stock 2/6 speed wheelset (or 3rd parties compatibleones) Compatible #X4UnibodyCogSetReuse your old wheelset (C Line) and expand to #WiderThanPTLine 4 speed gear range Features : CNC machined 4 cogs (11-13-17-21t) in One Unibody + 1.5mm & 1.8mm Circlip snap rings (MiniMODs)SCM440H heat treated steel. ED-Electrophoresis deposition surface processed blackMost efficient drive output, crispy clear shifting reaction9 spline Shimano spec, compatible with 2/6 speed Brompton (now C Line and Eelectric B : BWR hub) wheelset. You will need 3rd party longer Tensioner arm and Derailleur Chain Pusher upgrade.Compatible with most 3rd party 2 speed wheelset (MiniMODs, Hubsmith, H&H, Andoza, Joseph Kuosac, ORZ, RIDEA, Suncord ...) circlip snap ring or Lock nut type rear hub. 11 Speed and up (narrower) Chain required. Leading teeth on-shift design for ultra smoothness.Circlip type for maximum compatibility (1.5mm + 1.8mm custom snap rings included), also compatible with lock nut type rear hub.Not compatible with Sturmey Archer SRF-5 (W) 5 speed hub or Brompton BSR 3 speed, but compatible with SRF-5(N) 10 (5x2) speed hub, so 5x4 is possible Note: Older stock tensioner can only take upto 19t cog, so you will need a 3rd party (e.g. aluminum) tensioner, we have tested with MiniMODs, H&H, BooK, DCCH & Thx4ride (parallelogram derailleur), Suncord & RIDEA chain pusher type derailleur should work too. You will also need following upgrade parts (Not Included) : 4 speed thumb shifter (ideal brompton stock), 11 speed or up Chain.Disclaimer : X4 Unibody Cog Set was based on our pupular X3 Unibody Cog Set (easy DIY 2s --> 3s with most compatible stock parts). But for 4 speed mod, it will require other 3rd party upgrade parts (the derailleur tensioner system might be hard to adjust for some brands) and tighter precision requirement on Brompton rear frame (known to be not so precise since made manually).We will recommand this to be done in our dealer shops, Only order here if no dealer near and you are very confident with your own technical skillset. Stock 6 speed mod with X4 Unibody Cog Set on DCCH parallelogram derailleur (6 speed to 12 speed)

X3 Unibody Cog Set 3 cogs 11/14/17 for Brompton 2/6 speed wheelset (MiniMODs) 2S->3S or 6S->9S

Brompton X3 Unibody Cog Set (11/14/17T)

Stock 2/6 speed wheelset (or 3rd parties compatibleones) Compatible #X3UnibodyCogSet

Reuse your old wheelset (C Line) and expand gear range 11-17t /

Experience the 11t fast crusing speed about 10% faster

Features :

CNC machined 3 cogs (11-14-17) in One Unibody + 1.5mm & 1.8mm Circlip snap rings (MiniMODs)
SCM440H heat treated steel. ED-Electrophoresis deposition surface processed black
Most efficient drive output, crispy clear shifting reaction
9 spline Shimano spec, compatible with 2/6 speed Brompton (now C Line and Eelectric B : BWR hub) wheelset. You can keep most parts compatible (e.g tensioner, chain pusher, derailleur cable set). You do need a 11 speed chain and 3 speed thumb shifter upgrade which is not included in this listing.
Compatible with most 3rd party 2 speed wheelset (MiniMODs, Hubsmith, H&H, Andoza, Joseph Kuosac, ORZ, RIDEA, Suncord ...) circlip snap ring or Lock nut type rear hub.
11 Speed and up (narrower) Chain required. Leading teeth on-shift design for ultra smoothness.
Circlip type for maximum compatibility (1.5mm + 1.8mm custom snap rings included), also compatible with lock nut type rear hub.
Not compatible with Sturmey Archer SRF-5 (W) 5 speed hub or Brompton BSR 3 speed, but compatible with SRF-5(N) 10 (5x2) speed hub, so 5x3 is possible
You can also use it as a base for X3+1 application (i.e. add on larger cog and spacer to form a 4 speed set on a 4 speed free hub body. 19t / 21t is preferable. I will be harder to drive if larger than that)