3M Glass Short-Strand Fiberglass Filler Stage 2 — 2.56 oz Filler + 1 oz Hardener, Fast-Curing Waterproof Repair

3M Bondo Glass Short Strand Reinforced Fiberglass Filler Stage 2 is a fast-curing, waterproof repair filler designed to patch rust-outs, small holes and strengthen repairs on metal, wood, concrete and fiberglass.

This compact kit pairs a 2.56 oz can of glass short strand reinforced filler with a 1 oz tube of Bondo Red Cream Hardener so you can complete small but demanding repairs without extra reinforcement materials. The formula is stronger than typical lightweight fillers, sands quickly, and accepts most paints—making it a versatile choice for auto, marine and home repair jobs where durability and fast turnarounds matter.

How does this filler handle rusted metal and small holes?

The short strand fiberglass reinforcement gives structural strength to fills, allowing you to repair rust-throughs and holes up to about 1/2 inch without backing fabric or resin. It bonds to metal substrates and resists moisture once cured, improving longevity compared with non-reinforced putties.

• Reinforced formula supports rust-out and small hole repairs up to ½"
• Works directly on prepared metal after rust removal and primer
• Waterproof when cured—suitable for cars and boats

What is the working and curing time for this Stage 2 product?

Mixed with the included red cream hardener, the filler begins to set quickly, allowing you to sand in about 20 minutes under typical shop temperatures. Fast sanding reduces downtime and lets you progress to finishing or painting sooner.

• Includes 1 oz Bondo Red Cream Hardener for correct catalyst ratio
• Sandable in as little as 20 minutes when mixed properly
• Working time depends on temperature and hardener amount—follow directions

Which materials and repair stages is this product intended for?

This product is designed for the Fill stage of the 3M Body Repair System and is compatible with common substrates including metal, wood, concrete, masonry and fiberglass. It pairs with body fillers and glazing putties to complete a multi-stage repair workflow.

• Use during the Fill stage; pairs with body filler and glaze for finish work
• Suitable on cars, boats, trim, structural patches and some masonry
• Accepts most paints after proper priming and surface prep

How do I prepare, apply and finish this fiberglass filler?

Prepare the surface by removing loose rust, paint and contaminants, then apply the mixed filler to the damaged area with a spreader. Once it cures, shape and sand to profile before priming and topcoating for best adhesion and appearance.

• Clean and degrease surface; remove rust and loose material
• Mix filler with provided hardener in correct proportions; apply with spreader
• Sand to shape after cure, then prime and paint as needed

Who is this for: This compact Stage 2 Bondo Glass Kit suits DIYers, automotive hobbyists, boat owners and maintenance pros tackling small structural or cosmetic repairs. If you need a reinforced, quick-sanding, waterproof filler for metal, wood, concrete or fiberglass patches—and you value a product that integrates into the 3M body repair workflow—this kit is built for those jobs.