Rocket Sprockets Mini Rocket Sprocket Hub Mini Rocket Sprocket Hub To be used with #219 Rocket Mini Sprocket or #35 Rocket Mini Sprocket. The Rocket Sprocket Hub attaches to the Rocket Mini sprockets, and on to the axle. Different sizes available to fit axle: 30mm 40mm 50mm ... MSRP: Was: Now: $56.00 - $64.00 Compare