i got a guy who will sell me a 15x15x10.5 plexiglass box for 100 bucks, i have a flaming q audiobahn sub. wondering if any downside in this box?

Is it plexiglass or fiberglass?

i'm assuming it's a plexiglass/lexan box... are those dimensions it's external size, or the interior space? is it sized correctly for what your sub needs? incorrectly manufactured plexi boxes can crack, break, or leak around the seams. there are some other issues too... but you need to make sure it's sized right for your sub