Facom 3/8" Drive Long Spark Plug Socket - for 16mm (5/8") plugs. Knurled end for fast pre-tightening. Rubber grips to hold plugs in place. Extra long for recessed plugs - 9.8" (250mm). OD is approx 21.5mm .
Note - this socket has a matte/honed finish. The shorter socket has a chrome finish.