you remove from your Shimano XT M8000 11speed cassette 11/40 and/or 11/42 the cog 15T, 17T or 19T (depending on your needs) and you replace it with the ARI 48T upgrade cog, without any additional modification on your bikeyou remove from your Shimano XTR M9000 11speed cassette 11/40 the cogs 17T and 19T and you replace them with the ARI 18T cog given as spare component and you add, after the original 40T cog, the ARI 48T cog, without any additional modification on your bikefor your Shimano XT M8000 11speed cassette 11/40 and/or 11/42, we produce the optional 18T ARI cog to obtain a more fluent scalereplacement is easy and fast - see video attachedmaterial used is hard anodized ERGAL 7075T6all range of colors is available in our color chart at link Available colorsweight of 48 teeth cog is 122 grams