I use the fine grit black diamond, from Tractor Supply. I think I pay about $9 for a 40lb bag. They only sell coarse or fine. Not sure of the grit.
I got the coarse seems to clog the feed tube up, the small nozzle is to small it clogs fast, the medium one works the best so far. I got the coarse. I guess I need the small, the manual is worthless.















