Excellent cassette adapter for Shimano and Sram users who require that one more extra sprocket on steep climbs. Very simple to install, it fits behind 11-34/36 cassettes, displacing last cluster and one smaller sprocket. It saves on average 50g from your original cassette! 

This cassette adapter consists of 28-32-36-40T (154g) sprockets. It replaces your original cluster 28-32-36T (186g). It adds one bigger cog at the end, but still reduce weight and increase stiffness. You must also take off one more sprocket either 11 or 17T which decreases weight further.

Main advantages of using 4-cog cluster over single 40T cog are three-fold: Greater stiffness as a cluster, alloy freehub safety (15mm vs 4mm base) and huge weight reduction. After-market single 40T cog adds on average 50g to the original cassette, where absoluteBlack cluster takes off 52g. That is 100g difference!

Please note: rider+bike weight limit is 90kg (200lbs). This product is not suitable for shifting under huge loads as it may lead to deformation of teeth. Also, because it is CNC part it may not shift sometimes as crisp as original stamped cassette. Cnc'ed cassettes will always have a bit lower shifting performance than heavy steel, stamped cassettes.

For running a 1X system, please use 17px cage rear derailleur. When in use with 2x10, most recommended is long cage .