1. Use the grommets installation tool to knock the grommets together to repair or decorate leather crafts, belts or garments, the support mandrel is 16mm/0.63 inches, and the base size is 20.5mm*26mm (Diameter*Height)and the inner diameter is 16.5mm.2. Made of 45# steel, it has high strength, anti-deformation ability, and is more durable.3. The unique patterned surface of the mandrel has an anti-slip effect, allowing for a firmer grip during installation.4. The grommet tool set for repairing or decorating leather, clothing, handbags, curtains, and jackets. For use on eyelets on shoes, tents, awnings, canvas, tarps, and other fabrics.