Abstract: A connector closure cap of a medical fluid-conducting kit, in particular for supplying a nutritional solution, includes a base plate, which surrounds a substantially central through-opening and on a flat side of which a sealing sleeve, which projects substantially perpendicularly to the flat side, is arranged or formed, the internal cross section of which sleeve at least partly overlaps the through-opening in the base plate and is preferably coaxial with the through-opening. The through-opening is closed by a gas-permeable but liquid-impermeable, preferably planar, membrane element. The connector closure cap can be part of a medical fluid-conducting kit.