Proform pneumatic valve spring compressors are the prescription to cut cylinder head assembly and disassembly time in half. To use these tools simply pull the trigger for up to 350 lbs. of force with 125 psi (will operate on a minimum of 100 psi). The compressor arm will slide for adjustment, employ a locking pin, and you have fast, easy installation on most cylinder heads. With the valve spring compressed, the keepers and retainers can be easily removed. Pressing the pressure release button retracts the piston and sets the spring free. Removing valve springs can be a pain. Relieve the pain with the right medicine--Proform pneumatic valve spring compressors.