Nylon grommets are used for protecting wires as they pass through thicker panels of wood, metal, or other materials. When used correctly, they will prevent chaffing and eventual compromise of your electrical wires due to motion or vibration. Nylon grommets come in the following hole sizes: 1/8", 1/4", 3/8", 1/2", 5/8", 3/4", and 1" diameters. We also carry a universal grommet that can accommodate small to larger bundles of wire or cable up to 1/2" in diameter. The backside of the grommets have a 'retention' clip that will hold the grommet in place once inserted into the mounting hole. The black nylon material is smooth and allows easy pulling of your wires through the center.