These simple split stop collars add another level of usefulness to your Parf dogs. Each collar has a 38mm outer diameter and 20mm inner bore. They slide over your Parf dogs forming a temporary hold down. They are particularly useful for instance when biscuit or domino jointing boards. The rear of the board butts up against the Parf dogs with split collars preventing the boards from lifting. The split design will not mark or create burrs on the Parf dog. Supplied in a pack of two including hex wrench.-bg