We recently tested these fins on the advice of our friends Local Instructors, Ruth and Larry Harris. The Fins are the Hollis F2 and they appear as though they should be a prop in the next Rocketeer Film. A bit of steampunk thrown in with some Bio-Mimickery. 
Not Only Does The Fin Look Futuristic but it Performs as if Someone was actually thinking ahead.
If you are looking to reduce weight or just favor a lighter weight fin, The Stacked Blade, Hollis F2 fin is designed to add blade surface on both the downstroke and upstroke to increase your efficiency when Flutter Kicking.
These Bizzarro Looking Fins are light and shorter than a lot of the fins offered today.
The F2 is injection molded using monoprene which is lightweight material that makes it a great choice as a travel fin.
Rubber Fins are certainly heavier than Monoprene Fins and may be more desirable when wearing thick Semi- Dry Suits or Drysuits.
The Hollis F2’s are short so they pack well in your luggage. The Length also improves agility in tight areas. F2’s Come with adjustable stainless steel spring straps.
The Bottom View of the Hollis F2’s, what does this look like to you.
We recently tested these while diving dry in California and they are a little bit more bouyant than we needed for Drysuit diving. We think that they will perform so much better in a wetsuit at depth or in thinner wetsuits. Flutter Kick and all the other kicks ( Frog ) were easy to perform. We even found a slow back kick was do-able.
See The Link on HD’s Website.