Stainless flanges are needed for connecting different sections of a piping system in stainless steel. The flange is joined either by welding or clamping. The planar surface is turned or milled so as to facilitate sealing. Systems connected with flanges bring the advantage of ease of dismantling, e.g. for maintenance. The disadvantage is the risk for leaks. Stainless flanges with holes are classed according to system pressure; for example, PN16 designates an article for a maximum system pressure of 16 bar as stipulated in EN 1092-1. It is important that any two mating flanges are dimensioned for the same pressure class. For some dimensions, flanges without the central hole are stocked (“blind” flanges).