container 11 are located at the external peripheral junctions of the cap 12 and the container 11 to seal the interior of the container and cap from the exterior of the cap and container and thereby provide an ectosealing arrangement it is preferred that the sealing ring has a sufficiently small internal diameter that the sealing ring engages the container wall 23 so as to frictionally secure the sealing ring 13 to the container 11 thereby allowing the sealing ring 13 remain on the container as the cap 12 is removed from the container as a result the sealing ring 13 remains in a ready condition for sealing so that all the user needs to do is to screw the cap on the container 0031 fig3 is a detail view of the shoulder 14 on the container 11 supporting a sealing ring 13 therein which is compressed by an annular lip 19 on cap 12 the annular lip 19 comprises a sealing surface that engages the top side 13 a of sealing ring 14 similarly the shoulder sealing surface 14 engages the lower side of sealing ring 13 at region 13 b in the embodiment shown the axial pressure created by the threaded engagement of threads 21 and 22 allows one to compressively squeeze the sealing ring between lip 19 and shoulder surface 14 in the.