Get that hip, yet wise 40 or 42 tooth upper range, in a more economical form. The Sunrace CSMS3 10-SPEED Cassette might be your answer. It works on most current 10 speed systems from Shimano and SRAM, by simply replacing your current 10 speed cassette with this larger one. It's also a more cost effective way to go than the aftermarket expander rings, most of which can leave an uneven step in your cassette where another cog needs to be removed. This is a smooth and seamless block of cogs, designed for smooth and even gearing, while providing the maximum gear range. The 6 largest sprockets sit on 2 alloy carriers to help save weight and save your freehub from gouging. The cassette works with most medium and long cage rear derailleurs, but may require a longer B screw. FEATURESLightweight wide-range MTB cassette upgrade for HG splined (Shimano/SRAM 8-10sp) freehubsHi-Tensil steel cogs for durability and strength6 cogs on 2 aluminum spiders with polymer spacersSRAM derailleurs are generally compatible, Shimano derailleurs require a longer B-tension screwSpeeds: 10Range: 11-40T or 11-42TCogs: 11,13,15,17,18,21,24,28,32,36,40, or 11-13-15-18-21- -24-28-32-36-42Cassette Body Type: Shimano/SRAM 8, 9, 10 Speed , Shimano Dynasys 11 Speed Mountain