bondo Fiberglass Reinforced Filler Kit 1.37 lb with 0.5 oz Cream Hardener — Short Strand, Waterproof, Quick-Sanding

Bondo Short Strand Fiberglass Reinforced Filler is a fast-curing, waterproof body filler reinforced with short fiberglass strands designed to patch holes, rust-outs and dents up to 1/2 inch without backing materials.

This two-part kit combines a 1.37 lb tub of fiberglass-reinforced filler with a 0.5 oz (14 g) dose of Bondo red cream hardener for a strong, sandable repair that works on metal, wood, concrete and fiberglass. The added short strands provide higher tensile strength than traditional fillers while a slightly thicker consistency helps control flow on vertical surfaces for neater application. Use it during the fill stage of a body repair workflow and finish with glaze and paint for a durable, paint-ready surface.

How quickly will this filler cure and be ready to sand?

When mixed with the included red cream hardener, the filler becomes sandable in about 20 minutes under normal workshop conditions. Cure time can vary with temperature and mix ratio, so follow recommended amounts for consistent results.

• Sandable in as little as 20 minutes under typical conditions
• Fast drying reduces overall repair time
• Avoid low temperatures which slow curing
• Proper mix ratio ensures predictable set time

What types of damage and materials is this product suitable for?

This filler is formulated for patching rust-outs, small holes (up to 1/2 inch), dents and general body repairs on a variety of substrates. It bonds well to metal, fiberglass, concrete, masonry and wood when prepared correctly.

• Repairs holes and rusted areas up to 0.5 inches without backing
• Works on automotive panels, boats, and structural items like wood or masonry
• Can be used with standard body filler and glaze for layered repairs
• Waterproof formula suitable for exterior and marine exposure

How does the fiberglass reinforcement change performance?

Short interlocking fiberglass strands increase strength and resistance to cracking compared with conventional lightweight fillers. The reinforcement gives a tougher patch that holds up better under vibration and flexing.

• Fiberglass strands create a stronger, more durable repair
• Thicker consistency reduces sag on vertical surfaces
• Improved structural integrity for areas with movement or stress
• Compatible with typical automotive paints when properly primed

How do I apply and finish a repair with this kit?

Prepare the damaged area by removing rust, loose material and contaminants, then mix a small amount of filler with the cream hardener. Apply, shape roughly while workable, allow to cure, then sand, glaze and prime before topcoat.

• Clean and abrade the surface for best adhesion
• Use the supplied hardener—add sparingly and mix thoroughly
• Apply in thin layers for hole fills; build up as needed
• Sand, use glaze for fine imperfections, then prime and paint

Who is this for: This product suits DIYers, collision repair pros and marine technicians who need a stronger-than-normal body filler for spot repairs without fabric backing. It’s ideal when you want a waterproof, fast-setting repair for small holes and rust-outs on cars, boats, wood or masonry, and when a quicker, sandable finish is required to return the surface to paint readiness.