This set of pliers and spacer wedge was designed for easy valve adjustment. Plier tip pushes between the spacer shim and the camshaft as the pliers are squeezed close, while the spacer wedge maintains a gap between the shim and the camshaft as the pliers are removed. The spacer shim can be removed through this gap and replaced with one of the correct thickness. Made from quality heat treated alloy steel. Warning: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm.