The main concern in pneumatics is optimally designed overall systems without any leaks. That is why transfer points, such as those between compressor, lines, and hoses, are decisive. This is where couplings, sleeves, and fittings are used to connect perfectly harmonised system components individually with each other and protect them. The counterpart to a coupling is a plug-in nipple, for instance. A form-fitting connection between these two elements can provide a seal in one or both directions or hold the passage constantly open. Immediately after disconnection, the coupling seals to prevent medium leakage for safety reasons. The classic counterpart to a fitting is a sleeve. In combination, they create an uninterrupted connection between two pipe or hose ends.