This is the praxis works single speed 104mm bcd mountain bike chainring praxis have brought out these new single rings for people who dislike front derailleurs and just turn their cranks until smoke comes out their knee caps they begin with a 4mm 7075 t6 blank of aluminium and then stamp and machine the rings to perfection with ring tooth counts from 32t all the way up to 38t praxis have you covered dont be afraid rip that front derailleur off your bike and see how running a single up fro