The Finis Agility Paddle is an interesting piece of kit. Hand paddles are used for building upper body swim strength, they do this by increasing the size of your hand and therfore increasing resistance as you pull.
Most paddles have finger loops or elastic tubing which fastens them to your hand, by contrast the agility paddle doesn't. There's a small hole for your thumb to go through but nothing else to stop it falling off your hand! At first, it seems that these paddles won't work, but in practice, they do and they are very clever.
As you pull on the water, unless you constantly have pressure pushing the paddle against your hand, it falls off. This encourages you to catch the water better and to maintain water pressure on your palm all the way through the pull phase. It takes a couple of goes to get used to them, but after that, you figure out how to work them.
The beauty of these paddles is that not only are they a 'strength builder', they force you to pull with correct form, so they are a technique developer!