Restricted Top and Side Hung Window Friction Stays - Available in 13mm & 17mm Stack Heights. The restricted friction stays offer a quality and reliable replacement window hinge for your PVC double glazed window. Available in either 13mm or 17mm stack height, these handed friction hinges are normally replaced when there are gaps around the window, movement on the hinge side of the window, draughts or cold around the area of the window, clunky operation of the window or difficulty opening or closing the window. Supplied as singles, this item is available as either a left or right handed application. .