Slide Ring 180 Degree Inside Dia 229.26 mm Outside Dia 280.74 mm Number of Rail Holes 4 Mounting Hole Center to Center 255 mm Mounting Hole Size 5.5 mm Thread Size M5 Screw Type Socket Head Cap Screw Temp Range -20 to 60 Rail Material Steel Rail Finish Precision Ground For Use With FCP25255 Carriage Plate