Neewer Professional Aluminum Alloy Quick Release Plate Adapter with 1/4" and 3/8" Screw for DSLR Camera Camcorder Tripod Monopod, Campatible for Manfrotto 501HDV 503HDV 701HDV 577/519/561/Q5 With red safty pin prevent sliding accidently which can keep your camera camcorder safe With three bubble levels to help indicate how much of your slanting Rubber mat on surface prevent wearing of camera,campatible for Manfrotto 501HDV 503HDV 701HDV 577/519/561/Q5 locking knob makes quick release plate more stable and prevent loosing and sliding Holes in the adapter plate enables more connecting possibilities