Grinders are great but just don't buy a metal grinder because they break too quick and easily. Both me and my friend had a metal grinder and within the course of 3 months all the metal spikes had broken off inside. A small plastic grinder for about $7 at any local headshop works just about the best for a cheap price i have found. That's my opinon though, the plastic just seems to hold up better to the green.