I wore them on an 85 minute dive, they worked well on both kicks for me and offer good propulsion with both kicks, my buddy wore them on the second dive and he wished the were heavier (he used bat fins one dive 1 so anything would feel light after that) he also didn’t notice any improvement in the flutter kick but bats don’t flutter so I’m a little baffled by that but he is a 95% frog kicker and the bats excel at frog kicks.I’m also interested in the stiffness. Lexvil, when you tried them out how were they with different types of kicking strokes? Frog kick vs. flutter? Did they seem like they’d be good in strong current? Thanks!