Helix Core e*spec Direct Mount Chainrings feature our narrow-wide tooth profile, for reliable chain retention and an extra long wear life. Helix Core e*spec rings are cold-formed from steel and then heat-treated to provide excellent durability and toughness, all at a price that's easy on your wallet. - Long-lasting and economical steel construction - M4 narrow-wide tooth profile for excellent chain retention and Shimano(R)/Sram(R) drivetrain compatibility - Compatible with Sram(R) T-type(R) chains