All grab bars are fabricated of satin finish 18 gauge type 304 stainless steel tubing. In compliance with strength requirements of ADA Guidelines. Concealed mounting. Flange is 3" diameter, 1/2" deep, 11 gauge type 304 stainless steel with satin finish. Tenon plate is 13 gauge with slotted screw holes. Flange is secured to concealed tenon plate with 3 stainless steel allen head screws. 1 1/2" O.D.