These clamps are made from pure nylon for maximum strength and have rounded edges that won't cut into wire. They also have a unique screw hole alignment locking mechanism that prevents them from twisting when tightened by a mounting screw. Resistant to solvents, oils, acids, and moisture. They absorb shock and vibration and reduces unwanted noise. Black clamps have a UV inhibitor added.Wire Bundling per ABYC GuidelinesABYC (American Boat & Yacht Council) states: Conductors shall be supported throughout their length and shall be secured at least every 18" (455mm) by one of the following methods:By means of non-metallic clamps sized to hold the conductors firmly in place. The material shall be resistant to oil, gasoline and water and shall not break or crack within a temperature range of -34C (30F) to 121C (250F)By means of metal clamps lined with an insulating material resistant to the effects of oil, gasoline and waterAll of Ancors cable clamps are resistant to oil, gasoline and water and are rated for use within the ABYC-specified range.