The Gorilla Sea wing of the 90's was made of a stiffer material than the "Hyperthane" multicolored and black Sea Wing fins. The fins though stiffer, are not so stiff that there is no flex at it's pivot points (especially in XL form), however you will have to be a strong individual to maintain this. Advantages was that the fin is more versatile than the Original Sea Wing, allowing for an effective frog kick & scissor kick. An old video of me with these fins shows that they did pivot and Snap when using a strong flutter or bicycle kick. I used the Gorilla for a while and was reasonably satisfied but returned to the XL Jet fin as I find them to be the best all around fin on the market. The sea wing design was intended for a bicycle or flutter kick, that was the point of the pivoting notches and this is also evident on the new Sea Wing Nova's. I still have the Gorillas and I must say that they have held up very well, I tried not to leave them in the sun though...