HYPA Hubs are compatible with all known 7 Inch Tyres & 8 Inch Tyres on the market today. TRAMPA’s very own & genuine ABEC rated Bearings push perfectly into the HYPA HUB, guaranteeing the fastest spin rate possible. Use 12mm bearings (12x28x8mm) for 12mm axles or you can use Bearing Reducer Sleeves to fit your existing 12mm bearings onto 10mm axles (9.52mm or 7/16ths inch axles). 9.52x28x8mm bearings also fit TRAMPA hubs to 9.52mm Skate Axles.