1 Hole Short Barrel Copper Compression Lug w/ Peep Hole 1000 MCM - 5/8" Bolt Short Barrel Copper Compression Lugs with Peep Hole is a type of copper compression connector that is produced from high conductivity copper tubing. They are tin-plated to provide corrosion resistance and are marked with die index and color coded for easy reference. Listed for 35KV maximum when properly installed.