O-Lok fittings are designed to prevent hydraulic system outflow and allow higher operating pressures (630 bar to 12mm / 1/2" O.D. The O-Lok range of fittings is stainless steel, brass and steel. These fittings are used in many different sizes and wall thicknesses. These fittings can be used with both inch and metric tubing. One O-Lok fitting can hold multiple diameters of a tube by simply changing the sleeves or braze-on spud.