It's very hit and miss. I've had a Dremel-brand bit that on its second use, half the diamonds chipped completely off leaving bare metal. I've gotten a couple of the cheap multi-packs off Amazon, and while a couple of them aren't perfectly centered on axis, when you're paying $12 for 60 bits it's not too big of a deal if a couple can't be used. I'll probably buy the cheap pack again when I need more bits.