I recently gave a FM workshop, not with the intention of selling the slider. I did have one I passed around, comment from one student
" I did not see the difference when using it, until I did not have it anymore". She did order one.
Once she passed it on for someone else to try she found it HAD made it easier.
I was sold on it when it made FM soooo much easier with the fusiable batting against my machine. (no backing).
I don't have to tape it down to stay put, like I would think you have to do when using an alternative.