Knobbed Plugs are made of silicone and suitable for use screw holes from M3 up to M20. Knobbed Plugs are hollow, which allow for flexibility. They fit the screw hole perfectly, without any flange areas masking the area around. Knobbed Plugs have a tiered design, ensuring that they stay in place when installed. They also have a protruded feature at the back for easy grip and handling, so you can easily remove the plug.