Climbing Wall T-nuts, 3/8-16, Heavy Duty (.075 Material), 4 Prong Zinc Plated (500) Heavy Duty T-nuts for climbing walls, 20% Thicker than non-3Ball T-nuts Fits 3/8" bolts. Outer Diameter of barrel: 7/16" Climbing wall panels must be at least .75 inches thick Zinc plated for indoor / outdoor use. Each package includes 500 T-nuts