Which one should I buy, coarse (12 grit) or fine (24 grit)?
https://www.harborfreight.com/25-lbs-coarse-grade-walnut-shell-blast-media-92150.html
25 lbs. Walnut Shell 12 Grit Coarse Abrasive Media $24.99
https://www.harborfreight.com/25-lbs-fine-grade-walnut-shell-blast-media-92155.html
25 lbs. Walnut Shell 24 Grit Fine Abrasive Media $22.99
I also looked at Petsmart but they are more expensive and don't mention the grit:
https://www.petsmart.com/reptile/substrate-and-bedding/all-living-things-ground-reptile-bedding-24571.html
All Living Things® Ground Reptile Bedding 25 dry Qt $27.99