Alphacool's new quick-release coupling sets have been newly developed to offer extra security. For this reason, these couplings do not use a "click" mechanism but are bolted with a nut. The couplings can no longer be unlocked accidentally. The couplings affect the flow rate of your loop only minimally, or not at all. While unlocking, both sides of the coupling seal completely. They have a G1/4" internal thread on both sides so your choice of fitting can be used.