This adapter allows you to use roof and in-car carrier systems with a Quick Release fitting system. It is suitable for 15x100mm, 20x100mm, 15x110mm, and Boost 12x100mm. This adapter is compatible with the Peruzzo Roof Bike Carrier Pordoi Art.702 and Peruzzo Indoor Bike Carrier Genova Art.651. It fits almost all QR designed carrier systems and includes both 15 and 20 mm spacers. This is a special adapter for downhill.