Opening size is adjusted by manually rotating a high-friction bezel. Opening is square in shape, ranging in size from 1.0 mm to 8.1 mm (0.039 inch to 0.319 inch
Mount to your equipment with two screws, or by lightly pressing (with O-ring interference) into a bore.
The central opening is concentric with the cylindrical mounting surface, within a tolerance of about 0.006 inch (0.15 mm).