Alphacool quick coupling kits were developed for security reasons. For this reason, these clutches do not "click" mechanism but are bolted to a kind of nut. The couplings can be so not accidentally unlock. Through the installation of these couplings, the flow is very low not affected to do. When unlocking both sides of the coupling seal completely. There is a connection for 8mm ID, 11mm OD tubes on both sides. Please take care not to mix up the IN and OuT ports. On the "Eisbaer", the "outlet" is marked in "red" and the "inlet" in "blue". On the components to be connected, it is the opposite. The coupling with the "blue" marking denotes the "outlet" and the coupling with the "red" marking is the "inlet". This is important as in many coolers the flow direction is crucial for optimal cooling performance.