Axles for R45D rear hubs equipped with the original Twin Bearing driveshell systems. Not compatible with the current Gen 4 system. For R45D Centerlock, serial numbers starting with 671, and R45D Gen 2 6 Bolt, serial numbers starting with 691. PHB646(B) 135mm x 10mm QR R45D (Gen. 2) and R45D Centerlock PHB768(B) R45D QR Axle Insert PHB645(B) 142mm x 12mm R45D (Gen. 2) and R45D Centerlock PHB648 Rear: 135mm x 10 mm QR R45D Campagnolo (Gen. 2) For R45D Gen 1 6 Bolt with serial numbers starting with 651. PHB642 Rear: 135mm x 10 mm QR R45D Campagnolo (Gen. 1) PHB641 Rear: 135mm x 10mm QR R45D (Gen. 1, 11-speed) PHB643 Rear: 142mm x 12mm R45D (Gen. 1, 11-speed)