Narrow-wide Round chainrings for Cyclocross in 110 and 130BCD.Size (Mass +/-1g):130BCD: 42T - 64g ; 38T - 49g 110BCD: 42T - 81g ; 38T - 59gCompatibility:All 5 arm cranks with 110 or 130 BCDMaterial:CNC machined 7075 Txxx Aluminum. Long-lasting constructionFinish:Type II anodizingMounting holes:110mmx5 or 130mmx5Its specially designed wide-narrow tooth profile keeps the chain really snug, allowing you to leave your chainkeeper in the garage. It saves more than 100g on average by removing the chainkeeper and the bashring from your existing 1x setup, or more than 200g if using 2x drivetrain. Works with Clutch type and non-clutch rear derailleur.The chainring is optimized for running in the mud, having specially designed chamfers. Always use a new chain with a new chainring. Suitable for Singlespeed conversions.Chain options:10 or 11spd chain for geared bike or 6-8 spd for SS. If used in 1x9 drivetrain - 10spd chain must be used to obtain the performance. (yes - 10spd chain will work great on 9spd cassette)Chainguide needed?No, but chainlength is important as you don't run clutch type rear mech. Short cage really recommended.Important information for SHIMANO derailleur users.In order to get best results we recommend increasing cage return spring tension. New derailleurs are assembled with the spring in the mount that allows the most relaxed position of the spring. However there is another position on the cage which will increase that tension. It is a standard procedure.Sram users are not required to do that as oem springs are already in high tension position.