When tightening the joining clip two forces apply:
A) An axial force pushing the flanges against one another.
B) A radial force centering the flanges.
A few good reasons for ordering joining clips with gasket:
The gasket is applied under ideal conditions in our factory (no dirt, extreme temperatures or humidity usually found on the construction site).
Labor and time savings on the construction site
Fittings such as Elbows are easier to position adjust (no friction) without damaging the gasket.
Joining clips with gasket allow an easy disassembly of ductwork segments.
The air-tightness class C / ATC3 can only be reached when using joining clips SR with gasket.