In simple terms, the phrase "sealed unit" refers to something that is completely closed or sealed off, with no openings or gaps.
Sentences with «sealed unit»
I bought dual - detection 10 - year sealed units for my rental. (biggerpockets.com)
These systems turn roll - fed materials into fully formed, filled, and sealed units in short order — accurately weighed, marked, and shelf - ready. (fresco.com)
Because it's a completely sealed unit it's waterproof too. (pocket-lint.com)