Ống đựng kim tiêm Insulin

The top and bottom will fit very tight - so tight that it will be hard to put it.  You will need to put it on and take it off a few (maybe many) times for the fit to loosen up a little.  It will take a little work.  You want it to be tight so the top does not come off by itself.  When you pull the top of quickly it should pop like a cork.