stainless steel friction stay, 4-bar-hinge. durability and smooth operation. quick release levers allow window to be fully opened for easy cleaning and emergency escape restrictor mechanism autuomatically relocates or resets as the window is closed window hinges (friction stays)of different specifications, ranging from 2.0-3.0mm in bar thickness, 15-18mm in bar width and 15-22mm in groove width. we can also produce friction stays according to your own requirements