Black, light weight of cup wheel, Less pain 30# Grit Size, Rough Cutting Long and short segments Alternate Design, faster and smoothing grinding 5/16 inch (8mm) Segment Height, Durable Life Small Drilling Hole on the back side, it is Dynamic Balance Treated! 1 pc per Pack Can be used in any brand grinder in America For Sidewalk, Concrete Slab, driveway Grinding...etc. PLEASE NOTE: Small Holes on back side are Dynamic Balance Treated for cup wheel. Every cup wheel must be do Dynamic Balance before out of our factory.