A closure (20) is provided to selectively permit or restrict communication between the exterior and the interior of a system that has an opening between the exterior and interior. The closure (20) includes a closure body (24) that defines an access passage (30) and a membrane (60) that initially occludes the access passage (30). The connection of the membrane (60) to the body (24) is defined by a tearable portion (68) of material that defines a tear path along which the material can be torn. The tear path has; (A) a first separation path (80) where separation of the membrane (60) from the body (24) initially originates; and (B) a second separation path (90) where separation of the membrane (60) from the body (24) terminates. The second separation path (90) has a generally tapered configuration.