Basically, your glasssed on fin is one with the board itself. You cannot take it out. Basically it's resined and laminated into the board. After they laminate the board, they set the fin in and they put glass rope around the base of the fin, four layers of fiberglass up the fin and laminate it all in resin. Then that way the fin is glassed into the board. Good things about the glassed on fins it's not going anywhere, it's not going to break out, the base of it is very strong, and again it's one with the surfboard. The disadvantages of it you can't change you're fins out or travel with glass in fin is really hard because most of times it will break out in traveling. Most people who don't travel will use glassed on fin even on their thrusters because of the fact that it works as one with the board. That is glassed on fin.