The neosomething magnets used in superplugs, etc are much, much stronger than those sold for under $8 or that come with i.e., GM vehicles. You can buy these magnets in many different forms and sizes on the internet as they are used and resold from old computers.
I have a superplug for my motorcycle and car. The one for the bike is fine. The only problem I have with th auto plug is that is it a regular 3/4" bolt head with no built built in lip like most OEM standard plugs. This necessitates using the supplied metal/rubber gasket to ensure it doesn't leak as the bolt head doesn't cover the entire gasket not does is there enough head area to totally cover the supplied gasket. I called superplug and asked them about this. Their reply was that they use the metal/rubber gasket as they has leak problems with some of their bolts. I asked them about the design of the bolt head. Apparently, these use a common 3/4" bolt for many auto applications and modify the thread and magnet holder end for many applications. At my request, they did send me an extra 5 gaskets however.
If you get the superplug with the rubber/metal gasket, ensure you tighten it down, wait and tighten it down again several times as the metal/rubber gasket compresses. I didn't realize how much compression was going on the first time and when I went to change my oil, the plug was almost finger lose. From experience, the gasket will last about 2 oil intervals before it starts to fall apart and require replacement.
