Personally I think it is a unreliable gimmick, but since the fins are relatively inexpensive (I see them for
79€ for example
here) it may be worth buying them only for the foot-pockets (I did not find them yet individually for less than
71€
here). The fins certainly work relatively OK despite being gimmick, and even if they break apart after a while, you'll have excellent foot-pockets (and nice looking blades for your collection

)