With the Facom B.J21A1 spark plug socket, you remove and install 21 mm spark plugs smoothly and securely. Thanks to its 90 mm length, you easily access deeply recessed plugs located inside cylinder head wells. The built-in retaining system firmly holds the spark plug, allowing you to lift and place it safely without risking damage to the delicate ceramic insulator. Its standard 3/8" internal square drive fits your 3/8" ratchets and extensions perfectly, delivering reliable torque transfer for maintenance on automotive engines, lawn mowers, and small power equipment.