Abstract: A seal such as a releasably attachable upper seal for a trocar includes a rigid distal support, a rigid proximal support, a rotatable flexible seal having upper portions sandwiched between the supports, a movable ring disposed between the flexible seal and the lower support, and a generally non-compliant, but bendable protective guide attached to the inside of seal. The opening in the ring is sized smaller than the opening in the lower support. Cannulas and trocar systems employing such a seal are also disclosed.