You'll find these plates in 90% of commercial gyms. For the price they're definitely not worth it. Pain to deadlift with them. Not a bad option for machines if you can find them cheap used.
I've bought a handful of these over the years. Kind of a gimmick but it does feel a little better to do pushups and turn your wrist to adjust during the movement.
There are studies out there that support BFR training. The pump is nice but if you're looking for the real benefits from BFR training you probably won't find it from these.