E thirteen extended range ex cog 1x drivechains are everywhere you look this season from complete bikes to winning enduro rigs everyone is doing it so why should you have to miss out with the e13 ex cog range extender you dont have to simply fit this sprocket to your existing 10 spd cassette using the clear instructions provided and say goodbye to your front shift setup features its an add on cog to extend gear range of 10 spd shimano and sram cassettes it comes in 40t and 42t for u