For use in internal mast grooves designed for flat slides. These stops keep the sail and its slides in place on the mast above the slide entry gate. Just lock the stop in place with the knurled thumb screw. Made of heavy-duty, black anodized aluminum and marine grade nickel plated brass. Large knurled knob is easily released. The flat stop includes a hole for a lanyard. Size: 0.75" diameter x 1" length flat slide which has a thickness of 0.125"