Abstract: A weight plate having a detachable locking cartridge by which the weight plate is releasably connected to a lifting element (e.g., a center post) whereby one or more weight plates carried by the lifting element may be lifted by a user. The weight plate also has a plate body with a central bore in which to receive the lifting element. In one embodiment, the detachable locking cartridge is mounted flush against one side (e.g., the bottom) of the weight plate body so as to lie entirely external to the plate body. In an alternate embodiment, the detachable locking cartridge includes a stabilizer extension that is received within a cavity recessed in the one side of the plate body. The detachable locking cartridge includes a manually-accessible toggle lever switch arm that is adapted to rotate within a housing of the cartridge between locked and unlocked positions to thereby control the displacement of a locking pin relative to the lifting element within the central bore of the plate body.