Wolf Tooth Components 40t, 110bcd Drop-Stop Chainring, Black For maximum retention, utilize with a clutch-style rear derailleur Features Wolf Tooth's Drop-Stop tooth design for maximum chain retention Optimized for use with 10, 11, and 12 speed chains If riding in extremely muddy conditions, Wolf Tooth recommends a chain guide or chain keeper in addition to a clutch-style rear derailleur Made from 7075 Aluminum for long life