Safety cap for a cannula, comprising an outer sleeve (10) having a rolling end (11) and a top end (12) made of a rigid plastic material and a seal element (30) made of a gas-permeable, flexible plastic held inside the outer sleeve (10), having a channel (33) closed at one end to seal off the opening...http://www.google.es/patents/US6551286?utm_source=gb-gplus-sharePatente US6551286 - Safety cap for a cannula
