I have a bunch of different paddle fins, from Jets to Deep Sea Pulses that I use in the pool. They all work for frog kicking, but I don't like to use the soft ones (Pulses) in open water, because I can't generate much power with them. The stiffest fins I have are the Dive Rite EXPs, which are excellent for all the precision kicks but do take a bit more leg effort. Currently, my favorite fins are the Mares Power Planas, which seem to have the absolute perfect blend of stiffness and flexibility for doing precise kicking and also generating a ton of power when it's necessary.