Wolf Tooth Direct Mount Chainrings for Shimano E-Bike Motors have a 55mm chainline and are compatible with all Boost and Super Boost bikes that use the Shimano EP8, E8000, and E7000 e-bike motor splines. The Drop-Stop B tooth profile is compatible with almost all 9-, 10-, 11-, and 12-speed chains - the only exception is Shimano Hyperglide+. The Drop-Stop ST tooth profile is only compatible with Shimano Hyperglide+ chains. Direct Mount Chainrings for Shimano E-Bike Motors are machined with 7075-T6 aluminum at Wolf Tooth in Minnesota, USA.