I believe those yellow ones are plastic, the solid fiberglass ones are grey with a green line on them and ive seen them for 75 new,the best ones for a 100 have the honeycomb inside and they are blue and white. sorry if im mistaken,but unfotunately lost only gives out plastic fins with purchase of a new board probably only worth 30 or so
I think your right after looking at them more closely. Too bad for me I already paid him. Live and learn I guess, I wish you had posted this before I was dumb enough to buy them, lol.
Maybe exit will throw something in the package to make up for it. I did think they were the glass fins.