This deck umbrella mount stand are made of durable metal with a high-temperature powder-coated surface that is waterproof and rust-resistant; to install, simply attach the patio umbrella holder around the railing with straight-through bolts and tighten the knobs to lock the umbrella securely in place,This patio umbrella holder is suitable for 1-1 3/4 inch diameter umbrella pole,Patent No:222751582U