This are splitfins compatible with Mini Figures.
The fins has are without blade angle, so it is possible to stand with the fins. For a split-fins realistic angled blade look here:
Minifig Splitfins with angled blade
This fins has a split like modern splitfins.
The set contains one pair (two single fins).
Successful printed in FUD, Royal Blue Strong & Flexible Polished and Black Strong & Felxible.