The RB14-38X is a ring terminal insulated with high dielectric-strength nylon for wire range #18 - #14 AWG. Catalog numbers ending with the suffix X indicate an expanded insulation grip. This means a wider wire entry to accommodate heavy wall insulation. Ring terminals won't fall free even if the mounting screw loosens. Length 1.25 inches, .53 inches width, maximum insulation .190 inches, bolt hole 3/8". The terminal is high-conductivity electrolytic copper, electro-tin plated, with color-coded insulation. Recommended tool ERG4001.