Allstar Roller Bearing Style Camshaft Thrust Button for Big Block Chevy Timing Cover features a camshaft thrust button. It fits big block Chevy engines. It is manufactured from quality steel material and high quality roller needle bearings. The cam buttons help to limit lateral movement of the camshaft in engines without cam thrust plates. It helps to reduce friction for free horsepower. The machining of the cam sprocket may be required..