Wrenches (spanners) must not be used if its jaws are sprung, worn or cracked. They may slip off a bolt or nut when you least expect it.

The design of the bolt head insures that the bolt will not slip or rotate when the rubber is turned.

The SB series stuffing box cover combine the functions of wear plate and stuffing box into a one-piece replacement unit. One bolt holds the slip fitted stuffing box in place.