The cheap generic ones aren't bad. I have 2 of them and both are cheap, for $9 and $12, made of steel. The space cases are nice, made from aluminum. You're guaranteed quality with the brand name. However, like jrh72582 said, they're expensive. And that grinder you linked on ebay looks good to me. But, if you're buying online, go brand name and spend the extra money. If you're buying from a store or on the street, you wanna check for a few things in quality..
1. Is it smooth twisting?
When you open the grinder, make sure you feel the edges as you open it. One grinder I had, when I opened it, I could feel the unevenness as though it wasn't cut right. This is a buyer beware situation. I learned my lesson the hard way, lesson passed on. It's a silly thing because they are made by machines but someone has to set it up right.
2. Is it easy to close and open?
You did the open test, now the tightening test. Close it and TIGHTEN it as hard as you can. If it opens easily after you've tightened it, you've got a good grinder. If it doesn't open easily, it's because the threads aren't aligned properly allowing that extra space to further tighten it. You can always just try not to tighten it too much. But, guess how many times someone else has accidentally turned it the wrong way and actually struggled to open it, not realizing they're tightening it more. No more mistakes like that.
3. How big are the holes?
I've had grinders where the holes were so small the marijuana couldn't fall through. That's necessary if you're tryin to get the kif. It has to at least hit the screen first.
4. Is the magnet strong?
Hold the top part of the grinder by itself. Now, try to shake it out. If it falls right out, the magnet is weak and may cause you more trouble than it's worth in the long run. It's not so much of an issue with aluminum because that metal is naturally lighter. However, even my heavier steel grinder still holds pretty strong, 6 years running. The most recent grinder I got doesn't hold for shit and that one's actually lighter.
5. Is it a good size?
They come big and small but does it fit YOUR hand?? Comfort is always a factor.
Last bit of info. 3-part grinders are a blessing and a curse. Both of the grinders I now have are 3-part. I bought the first one so that I could get the kif. The problem was that the screen is placed up against the holes. So much marijuana got stuck between the screen and the holes. One day, I just knocked the screen out because I got tired of seeing so much stuck, I had a 4-part grinder (that I gave away), and I was out lol. The good thing about it is that the marijuana that fell through was the perfect consistency for rolling blunts. I stopped caring about kif so it was good for me.
So, if you want the kif, 4-part is the only way to go. 2-parts suck because the marijuana doesn't always come out so easily.
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