I couldn't find the link the other day.. but now I've got it.. They have 80, 180, 400 grit.. I have the 180.. and wish it was a little more aggressive but it works, My next one might be a 80 grit.. they tend to not be as aggressive as you think of for flat sanding paper
https://www.harborfreight.com/4-in-180-Grit-Abrasive-Ball-61184.html