These Praxis single 1X Cyclocross chainrings are based on a unique Wide/Narrow tooth profile for supreme chain retention in the roughest of cross conditions. These Praxis 1x 110 / 130 BCD chainrings are machined from 7075-T6 aluminium and Hard Anodized to take a beating.  Praxis 110 BCD wide/narrow 1x40t Chainring Version for 110BCD Compact or 130BCD Standard. Use with 5-arm crank, or 4 w/hidden 5th bolt SRAM Exogram crank. Mount chainring in outer position on crank. 42T or 40T Wide/Narrow tooth profile for better chain retention 10 or 11sp Shimano/KMC/SRAM Machined mfg 4.5mm plate 7075 T6 Aluminium for superior stiffness Hard Black Anodizing for longer wear SRAM BUILDS- Must be used in with SRAM 'CLUTCH' type rear derailleur. Example : SRAM Type 2 SHIMANO BUILDS – Since Shimano does not make a clutch road/CX type rear derailleur for use with their road shifters, please always use a chain guide device in very rough terrain, or just for pure security, we still recommend use of an upper guide