FRONT SPROCKET: 4057 K teeth number : 18 16CrNi4 Steel REAR SPROCKET: 2070 C teeth number: 43 Rear sprocket C45 steel CHAIN: 525XSO plates number: 104 Affordable and long lasting performance chain. RK's XSO chain offer less torsional friction and increased high-stress high -speed performance proving a longer lasting chain at an affordable price. All RX-Ring chain have "X" shaped seal and improved metallurgy giving you 7 times longer wearlife than standard chain