3M Wetordry Sandpaper 320 Grit – 9x11 in, 25 Sheets for Final/Between-Coats Sanding (99421NA)

Overview

3M Wetordry 320 grit sandpaper is a versatile choice for refining finishes, whether you’re performing final sanding or smoothing between coats. The 9" x 11" waterproof sheets are designed to handle lacquers, primers, sealers, plastics, and paints with a controlled, even cut. The silicon carbide abrasive stays sharp under use, delivering a smooth, consistent pass that helps you achieve a refined surface without gouges. This paper tolerates wet use, which helps reduce clogs and keeps the abrasive working longer, especially when working on detailed or contoured areas.

Two waterproof backings give you options for different tasks: a flexible A-weight backing for contour sanding and a durable C-weight backing for more aggressive stock removal. Whether you’re working by hand or with a sanding block, this sheet adapts to your workflow and helps you maintain steady control as you progress toward a premiere finish.

Key benefits at a glance

• 320 grit silicon carbide abrasive provides fast, smooth cutting for a refined finish
• Waterproof paper works well with water or cutting oil to minimize loading and extend life
• Two backings: A-weight for contour sanding, C-weight for material removal
• Suitable for hand sanding or use with a sanding block on flat or contoured surfaces
• Follow the grain where appropriate and skip no more than one grit between steps

Real‑world uses

• Prep surfaces for lacquer, primers, sealers, plastics, or paint to achieve a smooth base
• Address minor surface defects before priming or sealing for a cleaner finish
• Between coats smoothing to ensure even texture and attraction of the final topcoat

How to use

Maintain a light touch and steady motion, using a sanding block for flat areas. When working wet, apply a gentle stream or spray to reduce loading and wipe or rinse the sheet as needed. Transition to a finer grit as you approach the desired final feel for best results.