How easy is it to use them? Can they be used on the road or only on a trainer?
I let my 7y/o daughter swap my cranks for me. I do need to pre-loosen a couple things & then tighten them a bit more when she is done. Also, I adjust the front derailer because she doesn’t quite get it right.
If I do the whole thing by myself it takes about 20-30 minutes (depending upon how neat my workbench is). If I let my daughter do it, it usually takes about an hour.
I agree with goatboy. 20 min to swap out the PCs for regulary cranks and also swap my chainrings and pedals. Ideally, you’d have extra rings and peddles. Actually, if you have two bikes, have them set them up in identical positions to the millimeter and you have the ideal set up.