What he said, not the HF one. In fact, not most of them. The ones worth buying are from
Mag Switch! THEY ROCK! They are switchable magnets. The other ones suck when fabricating. They pile up with metal shavings that are hard to get off and can interfere with a ground. The
Mag Switch one, you turn off the magnet and pop it off, plain and simple. I've been running one on my Lincoln 251 for almost 3 years now, love it.
I only have found 2 issues. I wish I would have gone with the next size up one. The ground cable is so thick and heavy on my MIG that it pulls on the magnet a lot when fully extended, so just a bump can knock it off.
The other issue is, welding nuts. You know when you break a bolt, you weld a nut to it and run it out that way? Well with this that is more difficult to do. I generally end up holding the nut with a pair of vice grips then "clamping" my ground to the vice grips. Works well but more difficult than just having a ground clamp.
Other than that I LOVE them.
Matco sells them as does Mac, Snap-ON, Home Depot and a handful of other sources.
They also have some badass jig blocks. Great for setting up tabs, tubes, and all kinds of stuff. Check it all out.