Each size is a different from the next so here is how to tell if you have a correctly fitting jacket
If you can buckel the straps - you're in.... literally. The back does not need to be completly closed, that is what the straps are for, It's much better to buy a jacket that fits tight then loose.

Generally speaking, Up to 145 pounds, small - up to 190 pounds med and over that large, You can also use coat sizes: Up to a 39 inch chest, small up to a 46 inch chest med - over that large

If your jacket is NOT the right size (way to big) you can return it directly to the factory and they will exchange it.
If this is the case, the jacket must not be used. The exchange must be made within a few days. If the jacket is used, in any way, the factory will not exchange it and you will pay for shipping to get it back.

Good luck in performing you shows. Here is a performance tip: Pick out two pieces of music, one plays while you are put in the jacket. The other piece of musuc plays while you escape. I like to send the people back to their seats then realize that I have no way to play the music... then use my nose to start the music - always good for a laugh.

Magically,
Jay Leslie