Quoted from YeOldPinPlayer:
I think that's a bad risk. As an item designed to prevent a fire or other serious damage untested Chinese fuses have no place in my machines.
Since they're so cheap I'm sure you could do some testing yourself.
I probably wouldn't stick 'em in the line fuse but for backbox lights or something I wouldn't think twice about it.
It's not like you're watching the manufacture of any other fuse anyways, hell, all the fuses on those $50 "fuse kit" eBay listings probably come from the same place. If anything, I would figure the stereotypical "China quality" to be that they blow too easily. I never bought any myself - I ask friends for them under the rare occasion that I need new ones. Unless you're doing some fixing on a machine that really loves to shove some amps through the fuse block (burnt shorted coils... booooo. they blow 'em fast) I find that I'm decently good at making sure not to leave the machine on too long with something locked on. As for lighting, I think I've only blown one of those once, only way to really blow those in EMs is just being fairly clumsy. (if your machine is wired correctly and operating well of course, tracking down a problem is a different story of course!)
Other than that if a machine comes with one blown I either steal them out of another machine for testing or just buy what I need locally. I think Home Depot carries them now?