Billet Crankshaft Sprocket Has Three Keyways for +/- 4 Degrees Adjustability. Both Billet Steel Sprockets are Heat Treated for Durability. TRUE Roller 0.250" Roller Diameter "Z" Chain for Reduced Friction. "Z" Chain Approximately 33% Overall Increased Strength Over the Standard High Performance Chain. "Z" Chain Featuring a Press Fit Center Link design that Increases Load Distribution with Heat Treated and Processed Links to Maximize Ultimate Breaking Strength while Remaining Ductile for Toughness and Pre-stressed to Increase Fatigue Life. Includes Captured Needle Camshaft Sprocket Thrust Bearing to Minimize Block Thrust Surface Friction. 3-Piece Sets Hand-Matched to Qualify the Correct Center Distance and Minimize Runout.