SunwayFoto DDY-60p0 Discal Clamp for Arca p0 Ball Head, 60mm Diameter, Screw Hole UNC3/8", 44lbs Capacity SUNWAYFOTO brand Arca-Swiss compatible Accepts QR's from RRS Wimberley, Arca Swiss, Kirk, Markins, etc. Especially well suited for Arca-Swiss P0 Includes bubble level and the accessories pictured Diameter: 60mm