my experience with 420 science has been great. no complaints there. this grinder kinda sucks though. the teeth just don't really do anything. you put the herb in, twist, and it's stuck. doesn't shred without using a ton of force, which inadvertently tightens the lower chamber and makes it really hard to get apart. I have to break my herb into tiny tiny pieces, basically ore grinding the herb before I can grind it. my other grinders have no issues with the same herb