Tri grit sanding sticks grit sizes

Does anyone out there know or want to take a guess at what size grits are represented on a tri grit sanding stick?  When sanding a Revell 41 Willys body shell for instance, the three grits seem to do a very good job of removing mold seams, then removing scratches from that process, then smoothing and almost polishing plastic, but it would help in some cases to have greater surface area while sanding so I want to duplicate those grits with a larger pieces of sand paper.