This is a 1/350 scale version of the hangar deck seen the Star Trek V: The Final Frontier. It is for use in Round2's 1/350 Refit Enterprise kit. It's sized for use with the deck floor that comes with the model kit. Just trim it to the length you need.
The part is intricately detailed based on pictures of the full scale set as well as floor plans by Mike Okuda. It has several door ways with cargo barrels and the famous double-barrel laser prop. The top observation deck is fully detailed with an attachable rear wall.
This hangar is TWICE the length of the TOS hangar, so this is a biiiig part. Shuttles in the above examples are not included, but can be found alone
here, and in a set
here.