Designed specifically for use with Brose motor systems, this chainring is the lightest, most advanced e-specific ring ever designed. Pairing performance and design aesthetic to give you the highest-end E-MTB ring SRAM produces, the ring is also compatible with the SRAM Aero-Guard. Model: CR-XX-BR-D1 Steel and Aluminum construction. Compatible with Brose motor systems. AeroGuard Compatible that fufills EN 15194:2017 standard