Mine came with 20's, and they will work with broadheads. Sometimes you need a little longer bolt due to the field point not interfering with the rail, but the blades on a bh might. The way my rail is, a bh won't interfere, so I can still use 20's.
If you are buying it from a shop, get a bolt and lay it on the rail and see how much you would have for the bh. If you are ordering it online or through a sale online, wait until you get it and go from there.