3M 02018 Tri-M-Ite - Wet Or Dry Sandpaper Sheets, 9" x 11", 80/C, 50-Pack3M Wetordry Paper Sheet 431Q features extra fast cutting silicon carbide on a strong C weight, waterproof paper backing to provide superior finishing for both wet and dry applications on a variety of substrates, including paint, primer, gel coat, metal, and wood. Versatile sheet can be used wet or dry on paint, primer, gel coat, metal, and wood finishes Waterproof backing supports wet applications for decreased loading and a faster cut Strong C weight