Are Amazon fastener kits good quality or should I order from a specialist?

Mainstream reviewers and specialist subreddits split on this. Verified-purchase volume on the popular Amazon kits is enormous and r/3Dprinting threads concede they're a real deal for the price. But r/Tools and garage forums consistently recommend Bolt Depot or rural farm-supply bulk for anything load-bearing, because Amazon kits are typically Grade 2 or unmarked and not suitable for structural or safety-critical applications.