Yeah, those inexpensive little blue Chinese things work okay, but I haven't had the same experience with them as Geo. The construction quality is absolutely disgusting, as you'd expect for a $10 demagnetizer. Hell... the prongs on the plug are so thin, they make intermittent contact with the parts in your wall socket and sometimes fall out. My first one worked great over the year I had it, but I only used it maybe a half dozen times. It dropped dead the last time I used it. The second one didn't work right out of the box. I managed to fix it, but I'm going to purchase the Vigor unit from Ofrei. It works like the Elma, using a capacitive discharge rather than a continuously varying field, so no need to remove the part slowly until it's clear of the magnetic field. There's also a tunnel for demagnetizing tweezers, screwdrivers, etc. And, it's US made. Most folks probably wouldn't use it enough to justify the $270 price tag, but I will. For me, the Chinese cheapies are a case of false economy.
Stu