I am so glad I bought these swimming fins for my son. He's on the swim team at his high school, and he swims every morning for two hours. I recently bought him a kickboard, but he also needed a good pair of flippers so he can practice his kicks. His last pair is unusable because it tightened on the back with a strap, which broke within weeks. It is a slip-on flipper, so you don't have to worry about broken straps. It is made of durable silicone and my son says they fit great and are true to size. He says they are very comfortable, unlike his old pair where the back strap was too tight and chafed his skin on the back of his foot. These swim fins are helping him perfect his swim kicks and he is extremely happy with them. They are amazing for the price that I paid for him. I would highly recommend these swim fins to anyone looking for a pair.