The Sunwayfoto DDY-64i Discal Clamp 64mm With Short Handle is a Arca-Swisse compatible integral screw-knob clamp with an anodized black finish. It has a captive knob, safety-stop grooves, and a hollowed-out design that reduces the weight of the clamp.  You can use an M6 screw to mount it to an AS-style ball head, and it will accept any standard Arca-Swiss quick-release plate. This Discal Clamp also has an integrated bubble level.