Choosing the right grit at every stage is the difference between a flawless finish and hours of rework. Here’s your definitive guide to the Super Assilex and Buflex system, from coarse bodywork all the way to showroom-ready clear coat.

Grit Selection Changes Everything

In professional automotive refinishing, abrasive selection isn’t a minor detail; it’s the foundation every coat of paint is built on. Choose too coarse a grit, and you leave scratches that bleed through. Choose too fine, and you waste time removing material that needs to go.

Super Assilex and Buflex systems represent the top tier of dry-sanding technology.

This guide maps every grit in both systems to the exact stage of the refinishing process where it belongs, so you never guess and never rework.

Super Assilex

Super Assilex reduces sanding time by up to 50% with double anti-clogging technology and ultra-flexible bonding from old paint to clear coat; it handles every stage of the process.

Dry Sanding System · K240 – K1500

K240 – Putty & Body Filler Sanding

The starting gun of the refinishing process. K240 is your go-to grit for knocking down fresh body filler and putty, shaping the surface before primer goes on. Its coarser cut removes material quickly while still leaving a more controlled scratch pattern than conventional abrasives. Also effective for scuffing old coatings on wood substrates.

K320 – Edge Sanding & Initial Primer Work

K320 is ideal for sanding edges of body panels where flexibility matters most. Super Assilex’s latex backing conforms naturally to curved and complex surfaces, making it particularly effective on door edges and sills. Use it to refine putty lines and step down from K240 before primer application.

K360 – Primer Leveling

Once the primer has cured, K360 begins the leveling process. This grit flattens high spots left by primer build-up and removes any texture irregularities. It’s the workhorse grit for getting primer surfaces flat and ready for the next refinement step, cutting efficiently without creating scratches that are hard to remove later.

K400 – Primer Intermediate Sanding

K400 refines the scratch pattern left by K360, working the primer surface closer to a finish-ready state. Its uniform grain distribution, courtesy of Kovax’s roller coating manufacturing, produces consistent scratches that step down predictably. Especially useful when transitioning from an aggressive primer surfacer to a smoother base coat-ready surface.

K500 – Primer Finishing Before Base Coat

K500 is where primer sanding transitions toward finish work. At this stage, you’re refining the surface to accept the base coat or color coat properly. The shallow scratch pattern from Super Assilex at K500 ensures that primer scratches won’t telegraph through the topcoat, a common issue with conventional abrasives at this grit level.

K600 – Pre-Topcoat Surface Prep

K600 bridges the gap between primer finishing and topcoat application. It removes the last trace of coarser scratch patterns and creates an ideal anchor profile for base coat adhesion. At this grit, Super Assilex’s anti-clogging double coating becomes noticeably valuable; the sheet cuts longer and stays cleaner in production environments.

K800 – Topcoat & Clear Coat Sanding

K800 is where topcoat work begins. Use it to sand clear coat, remove dust nibs, or scuff existing finishes for re-coating. Its fine cut leaves a finish equivalent to a much finer conventional paper; that’s the K-number advantage Kovax is known for. K800 is one of the most frequently used grits in professional body shops for clear coat leveling.

K1000 – Fine Clear Coat Refinement

K1000 is a precision grit for stepping down clear coat scratches left by K800, particularly in touch-up and spot repair contexts. It brings the scratch depth to a level where the transition into polishing is smooth and predictable. Ideal for blend zones and panel edges where overspray blending meets the intact existing finish.

K1200 – Pre-Polish Clear Coat Sanding

K1200 produces an extremely fine scratch pattern that drastically shortens polishing time. At this stage, you’re removing any orange peel remaining in the clear coat and refining the surface so that compounds do minimal work. Super Assilex at K1200 is frequently the final sanding step before transitioning to the Buflex system or directly to polishing compound.

K1500- Blending Zones & Final Sanding

The finest grit in the Super Assilex range. K1500 is specifically designed for blending zones, the transition areas where fresh clear coat meets the undisturbed original finish. It removes fine orange peel, polishes blend transitions, and leaves a scratch pattern so shallow that the Bufflex finishing step or light compounding brings it to a gloss with minimal effort. No scuffing compounds needed.

Super Buflex

The Buflex system is designed for final surface refinement before polishing, producing extremely shallow and uniform scratch patterns.

K2000 – Pre-Polish Scratch Removal

K2000 Buflex is the entry point of the Buflex dry finishing system. After sanding with Super Assilex K1200–K1500, K2000 refines any remaining sanding scratches with an ultra-shallow pattern that compounds can remove in a fraction of the time. Its flexible latex film and specially formulated soft pad work together to remove topcoat sanding marks effectively without introducing new damage.

K2500 – Fine Polish Preparation

K2500 bridges the gap between K2000 scratch removal and the final K3000 step. It cuts buffing time dramatically on light-colored vehicles and high-solid or hard clearcoats where compound polishing is time-intensive. Roller-coating technology distributes grain with exceptional uniformity, so the scratch pattern it leaves is perfectly consistent across the entire panel.

K3000 – Final Pre-Polish Step

K3000 is the finest Buflex dry grit and the closest step to a polished finish possible with an abrasive film. It leaves scratches so fine that polishing time is reduced by 50% or more compared to conventional wet sanding approaches. Buflex K3000 also maintains the original paint texture, which is critical on modern anti-scratch clears and fluorine clearcoats where texture matching is mandatory.

K-4000 – Super Buflex Purple

For scratch-resistant clear coating. By hand polishing with the special pad, you can achieve a finish equivalent to P4000, and by using a polisher, you can achieve a finish equivalent to P5000. Buflex Dry is used to refine any last scratches before polishing after removing surface irregularities and imperfections. The K-4000, being the finest grade, sits at the very end of the sanding sequence; it’s the final pre-polish step that minimizes polishing effort to its absolute minimum.

KOVAX‘s Super Assilex and Buflex systems aren’t just abrasives; they’re a complete, stage-matched sanding workflow. When you follow the grit progression, the system rewards you with dramatically shorter polishing times, fewer reworks, and a finish that speaks for itself.

FAQs

1. What is grit size?

Grit size tells you how rough or smooth the sandpaper is. Lower numbers are rough and remove material fast, while higher numbers are smooth and used for finishing.

2. What grit is used for primer sanding?

K400 to K600 is used to level the surface, and K800 is used to make it smooth before painting.

3. When should I use Buflex?

Buflex is used after K1500 or K2000, just before polishing.

4. Do I need to use all grits?

Not always, but skipping too many steps can leave scratches.

5. What happens if I use the wrong grit?

It can cause scratches, a poor finish, and more rework.