WingIt Grab Bar Fastening Systems are made from 18/8 Stainless Steel and can be used in most hollow wall construction (see Installation Instructions). Typical straight Grab Bars use two GBW40s. WingIts become waterproof as they are installed into the wall. GBW40s can be installed into wall substrates (tile, drywall, etc.) up to 1.5" thick. GBW40s use 3M's best waterproofing adhesive to install completely waterproof in minutes. 1.25" hole required for installation - use our carbide hole saw. Use the WingIts Grab Bars. (GBW40 sold in singles)