Silverock Bike Bcycle Boost Hub Adapter Boost Hub Conversion 12mm x 142mm to 12mm x 148mmFront(15mm x 100mm to 110mm), Rear(12mm x 142mm to 148mm)Features of Silverock Bike Bcycle Boost Hub Adapter Boost Hub Conversion 12mm x 142mm to 12mm x 148mm Material: alloy 6061,CNC made | Rear 12mm boost hub adpater, Convert 142mm to 148mm | Include: 2pcs sp..