Hard plastic skeg fin set made for soft SUP boards. This thruster set up includes one 5” center fin, two 4.25“ side fins and six 3” stainless steel screws with plastic washers to attach the fins to your SUP. This will not work for SUPs that have a fin box. Side Skegs: Distance between screw holes on skeg: 4 inches Skeg length from front to back along the base: 5 inches Skeg height from base to tip: 4.25 inches Center Skegs: Distance between screw holes on skeg: 4 inches Skeg length from front to back along the base: 5.5 inches Skeg height from base to tip: 5 inches Screw length: 3 inches Specs: Maximum board thickness these will work with: 3.25 inches If you have a board thicker than this, please contact us via email or phone for an alternative. TIP: We highly recommend applying some dish soap to the screws before installing and screwing them into the skegs to make the process easier.