A cannula top for enclosing a surgical seal. The top comprises a base member 84 having a through bore which defines a receptacle for the surgical seal and a lid member 82 having a through bore. The lid is movable between a first (open) position in which the seal can be inserted into and removed from the receptacle, and a second (closed) position in which the seal is engaged by the lid and retained in the receptacle by the lid. A connecting member 86 joins the lid to the base in both positions and restricts separation of the two parts. The lid may pivot away from the base on the connecting member. The seal may comprise a lower duckbill style element 22 and an upper annular element 24. The lid and base may engage via threaded sections 98,100.
