CRV STELL   SPARKE PLUG SOCKET FOR 16 MM AND 21 MM BOTH SIZE AVALIABLE SINGEL PC PACKING.The spark plug socket is designed specifically to remove and replace spark plugs. It is deep enough to accommodate a spark plug and has a flexible sleeve inside it to grip the spark plug and permit one handed operation. Since various size spark plugs exist, a variety of spark plug sockets are available.