Puma, Its around 20 inches long. They tried to keep most of the ship models under the 22" mark set by the Enterprise kit from the First movie.
In the past, I built the Kazon ship, a fully lit DS9, a studio model Klingon BOP, the Original Series Bridge, some figures, and a fully lit Ent-A. Unfortunately, only the figures and Kazon ship survived. I do still have pics of the BOP though. And I plan on rebuilding it. This time with lights, and landing gear. And I have the Enterprises from ST:2, 4, and 6. And the cut-away Enterprise. And another DS9, which wont be lit, but it will have ships docked.
Now in CGI I have built much more. Including roughly 15 bridges, a shuttlebay, and a few other odd rooms and a couple ships.