The flex characterstics are controlled by tapered ribs on the sides and bottom of the fin. Flips flex is designed to catch a lot of water and push it behind you to propel you. The area of the fin that bends is the Flipper Area. A footpocket swimfin flexibility gradient only allows bending to start from in fron of the swimmer's toes. Flips Flipper Area is larger because they bend from mid-foot.
More work is required to move heavy fins through the water.
Flips swimfins are only 7 ounces each. A pair of Flips weigh less than half of most other swimfins. Flips , because they are fin blades with a harness, are very lightweight and flat. They are the perfect travel fins. Flips will fit in your backpack, garment bag, or suitcase.