Set of 4, screw out socket mount. 2" diameter x 7/8" Ruberex wheel, double ball bearing, split level, nickel plated steel construction offers superior swiveling and weight dispersion. Friction grip stem is precision formed and securely shanked to prevent wobbling. Each caster comes complete with amp cabinet receptacle and four 14-1 round phillips head wood mounting screws. Installation requires drilling a 5/8" hole in amp cabinet. Maximum recommended weight is 80lbs per caster.