Made of steel for long lasting use with a rust and corrosion resistant oxide coating. The surface of each part is smooth to provide safe, reliable operation under high compression. Easy to use - Close the coil spring compressor until you touch the center rod, then insert the compressor into the coil spring. - Compress the spring to install or remove it, and release the compression only when the spring is properly positioned for installation. - Note: The compression spring stores significant energy and must be handled and decompressed with care. Kit and storage - Includes 5 adapters in different sizes to fit various spring diameters for a secure and easy compression. - A complete 10 piece set is neatly packaged and organized in a plastic box for convenient storage and transport. Function and compatibility - Five adapters of different sizes fit different spring diameters on most cylinder heads. - The set allows correct spring mounting and makes the compression process easier. Use scenarios - Valve spring replacement on most automotive engines. - Cylinder head service on motorcycles, lawn mowers, generators, and other small engines. - General valve spring installation or removal tasks in a workshop setting.