For practical reasons Luka has agreed with suppliers or manufacturers to use the equivalent length of 1 metre for all circular fittings as well. This to the extent that the technical execution allows it and the actual length is smaller than 1 metre.

The formula for the maximum amount of air leakage for each round fitting that meets airtightness class C is:
øL/app = f.Ps .0,65(π x D).L Where: D = diameter in metres