The PDF fins we recently ordered were to replace the ones we have had for about 7 years.  We wore the others out.  We find them especially useful to help beginners that are having a hard time learing the breast kick.  They are also good for kids who have trouble finding the "right fit" in long training fins.  They make them work a little harder too, which is a plus.

she uses them for swim practice

These are great fins.  Lighweight for travel.

I bought these for a positive drive in my breast stroke kick, but i feel they work better for fly kick! They kill the top of you ankle because that is where the fin is, so if you do a  flip turn, when your feet are planted on the wall it hurts cause it pushes on your ankle veins.  However a did feel that these helped finish my kick, and a got  small push off of them.

Good. They really can be used for us Breaststroke kick challenged. You can use them for all strokes, they don't "give" like traditional fins, so they are great for resistance-building your FR kick.
Bad.If you have any kind of foot injury, ingrown toenail etc, forget it ! It hurts like heck with the close fitting fin. I suggest fin socks or wrapping your injury in a bandaid for a cushion.

this product fits great and is adjustable.  Me and my swiming buddies all where them and we have very different size feet.  They are very easy to adjust to you perfect size.  They give a great workout.  I use them for kicking and swiming.