The Mirka 40-663-040 Grip File Sheet is a coarse abrasive file sheet for bodywork, paint prep, filler shaping, and general heavy sanding. This is a sanding sheet designed for coarse material removal and surface prep. Model Number: 40-663-040. With its 16-1/2 inch by 2-3/4 inch format and 40 grit aluminum oxide abrasive, it is aimed at users who need fast cutting action more than a fine finish.

What matters here is how it works in rough prep stages. A 40 grit sheet is for knocking material down quickly, not for final finish sanding. That makes this sheet a practical choice for cutting through lacquer, leveling putty, cleaning up welding seams, and working on glass reinforced polyester where slower abrasives waste time. If the job starts with heavy correction, this is the kind of grit you reach for first.

Mirka backs the abrasive with reinforced paper to improve grain support and durability. In real use, that means the sheet is better able to keep cutting without the edge breaking down as quickly as lighter backing materials can. The product description also calls out reduced edge wear and minimal clogging, which matters when you're sanding filler, coatings, or other materials that can load up a sheet and kill performance early.

The semi-open coat is another practical detail. It helps produce a more consistent scratch pattern while resisting loading, so the abrasive stays useful longer during coarse sanding. That is especially helpful when you're doing long strokes on a file board or sanding block and need the cut to stay even across the full length of the sheet.

Because this is a grip file sheet, it is intended for sanding tools or hand sanding setups that accept grip-style file sheets in this size. The long narrow shape makes it well suited to straight runs, panel repairs, and surface leveling where a standard round disc is not the best fit. The paper backing also gives it enough flexibility for rounded surfaces while still supporting aggressive cutting.

Who should buy it? Auto body techs, painters, metal fabricators, and serious DIY users doing repair prep will get the most out of it. If you need a fine finish-ready sanding sheet, this is not that product. If you need a Mirka abrasive sheet that removes material quickly and stands up to coarse sanding work, this one makes sense.

Mirka 40-663-040 Grip File Sheet Means Business

This is the kind of abrasive you buy when you need to remove material now, not baby the surface.

• Who it's for: Auto body techs, fabrication shops, painters, and DIY users doing rough shaping and repair prep.
• Why it stands out: The reinforced paper backing, semi-open coat, and coarse 40 grit setup are built for aggressive sanding without giving up durability too early.
• Worth knowing: This is a rough-prep sanding sheet, so plan on following it with finer grits if the job needs a finish-ready surface.

• What kind of abrasive is used on this sheet? It uses aluminum oxide abrasive.
• What grit is this sanding sheet? It is a 40 grit coarse sanding sheet.
• What jobs is it suited for? It is intended for coarse sanding tasks such as lacquer sanding, putty shaping, glass reinforced polyester work, and welding seam cleanup.
• What size is the sheet? The sheet measures 16-1/2 inches long by 2-3/4 inches wide.