These paddles actually do what they set out to do, which is help you to improve your swimming stroke techniques. They are so simple to use, and can be used for all four strokes.
It is nice that there are no straps or elastic to fiddle around with, especially when other people may wish to give them a quick try as well!
I would be tempted to give these a five star review if it were not for two things. Firstly, I can't see that they'll get a great deal of use out of them, as once you have improved your technique they may only be required every now and then in order to check that you haven't gone back to old habits. Secondly, there may be only limited times when you are allowed to use these in your local pool, as many pools do not allow them in during normal public swim sessions.
Despite this, they do what they set out to do, and I recommend them for this purpose.