Abstract: Compression molding apparatus for molding plastic closures for containers includes a rotary turret having a vertical axis and supporting circumferentially spaced and axially moveable opposing plungers each carrying a compression mold member. Each mold member is attached to its corresponding plunger by a quick change locking coupler including a cylinder with circumferentially spaced holes supporting balls for radial movement. Each mold member has an axially projecting stud with an enlarged head portion projecting into the cylinder, and a cup-shaped piston surrounds the cylinder and has a recess for receiving the balls in a released position. A spring urges the piston to a locked position with the balls engaging the stud, and a housing is recessed within the plunger to support the piston for axial movement against the spring to a released position in response to pressurized fluid received within the housing through a passage within the housing and plunger.