Southco Inc R6-22-11 Fixed-Installation Concealed Hinge 90 Door Stay, Southco Fixed Installation Concealed Hinges - Concealed Hinges Fixed Installation - These hinges are available in 90, 180 and 90 with stay open feature. They are either Type 300 series stainless steel or zinc plated steel. Both steel and stainless steel come with black acetal washers and bushings. Panels over .16" thick will require a 45 chamfer. Install with either M5 or No. 10 hardware, or weld.