You obviously dont work on boats, where every bolt and screw is made from stainless and doesn't stick to magnetic screwdrivers. If you look closely there are actually ribs molded in that grab the heads of the screw. I've tried hose....it doesn't work that well. I've also tried tape, it does work well...once.
If you haven't watched the video you should. At least watch the hula girl demo, it's entertaining.
Or brass screws. The internal rib design looks like a sound idea. I agree that tubing does not work.
Anyway, magnetizing only works well on self centering drives. It's awful on slotted screws that wobble on the driver tip.
I've got the Klein/Vaco version for slotted screws.
I've got the split shaft drivers (a bunch of them). They're ok, but they pop off easily, and are only good for low torque screw starting. Also only good for slotted screws.
I also have the claw type (Craftsman, but the plastic claw Wera works the same way). Don't really like it. Same with the plastic cup Greenlee.
I like the Ullman spring loaded twistie ones on slotted screws. The Phillips drivers are aweful. And again, only low starting torque, or they pop off.
Honestly, these look like a nice idea, but not something I'd order online.
If I saw them at a hardware store counter for 50 cents, I'd grab a few.