Abstract: A fluid pressure operated chuck is provided with a stationary slip ring mounted on an axially rotatable chuck body, and a resilient sealing ring is located in substantially opposed grooves in the slip ring and mounted therein by temporary deformation of the resilient sealing ring during fitting, in the absence of fluid pressure. The sealing ring may be of a squat "T" section with the flanges at the head of the T providing marginal edge parts for location in the opposed grooves and the broad base face of the stem of the T forming a sealing contact face. Valve means are also provided in the chuck body to control the fluid pressure which latter acts on an axially displaceable piston to operate the jaws of the chuck.