The shimano 1x11 xtxtr expander sprocket kit from one up components consists of 2 replacements cog one 18t and one 45t this increases the stock shimano 11 40t cassette range by 125 percent and allows you to increase your front chainring from 30t to 34t without losing any low range the kit tunes the cassette into 2 distinct zones climbing 21 45t and descending 11 18t the 18t cog provides more even cassette progression for smoother cadence and both cogs have 10 upshift points available