DogBone, working on a great responce, forgot how we had to hand trim each pair of Force Fins. Polyurehtane is 6 times more abrasive resistance that steel, and is used in mining operations. Touch stuff, I liked to saw into a plastic fin and cut in half qickly..will make a video for you to show how tuff we are. Had to keep our trimming tool sharp with sandpaper. Ran the tool into my hand many times, trimming. 12 minutes to trim one pair. At the time we were moving 200 pairs each day out the door. That's 400 fins to trim. Many times Robert Flores and I had to come down from our shop and help the crew trim. I must have trimmed over 200,000 Force Fin parts. Anynew designs were mine to trim. This Trimming operation took real skill and many steps. I am warmed up on this subject...Passion to do the right job yourself if need be,