The friciton hinge made of Stainless steel201 or 202 or 304 with 4 bars pole.they have two items of common and square slot by heavy duty and friction with many series for more than thousand specifications, such as small slot (12mm,13.5mm,15mm); narrow slot ( 18mm), mid slot (20mm), wide slot (22mm), widen slot (27mm), from 6? to 38? specifications suitable to the uses of various section steel and Al alloy.