What Is FRP? The Real Guide to Fibreglass Body Kits for Aussie Car Guys

If you have spent any time looking at aftermarket front bumpers, side skirts, or spoilers, you have run into the term FRP. It stands for Fibreglass Reinforced Plastic, and while it is the backbone of the custom car scene, there is a massive amount of internet myths about how it actually works.

At Monkey Warehouse, we see a lot of kits. We know that the difference between a dream build and a panel-gap nightmare usually comes down to understanding the material you are buying. This guide is the no-nonsense breakdown of what FRP is, why we use it, and how to make sure you are not buying a dud.

1. What Actually Is FRP?

Think of FRP like reinforced concrete, but for cars. It is a composite material where layers of glass-fibre cloth are saturated with a liquid resin. When it cures, it becomes a rock-hard, lightweight shell.

Why do we use it instead of factory plastic? Factory bumpers are usually injection-moulded ABS or Polyurethane. That is great for mass production, but the tooling costs are huge. FRP allows the creation of aggressive, sharp lines and "time-attack" style aero shapes that standard plastics often cannot hold without sagging or excess weight.

2. Hand-Laid vs Chopper Gun - The Make-or-Break Choice

Once you understand the basics, the next thing that decides whether a kit is worth buying is how the FRP is actually made. This is the difference between a part that lasts and one that fails.

Hand-Laid FRP - The Monkey Warehouse Standard

Each layer of glass cloth is manually placed into the mould and rolled out by hand to remove air bubbles.

• The result: Consistent thickness, stronger corners, cleaner edges and lighter weight.
• The tap test: Flick the panel with your fingernail. A quality hand-laid part will have a sharp, high-pitched "click".

Chopper Gun FRP - The Cheap Import

A machine shoots chopped-up glass strands and resin into a mould. It is fast and cheap, but it is often messy and inconsistent.

• The result: Brittle sections, air pockets and uneven weight that can lead to cracking the first time you kiss a speed bump.
• The tap test: These usually give a dull, hollow "thud" because of inconsistent density and trapped air.

3. The Pre-Fit Rule - Why It Is Not a Defect

We get this a lot: "Why does it not just bolt on exactly like an OEM part?"

Here is the reality - FRP is a custom material. Even premium hand-laid kits require a "dry fit" before any paint. Every car is slightly different due to factory tolerance, age, previous repairs and even bumper sag over time.

A proper install involves:

• Test fitting: Bolt it on dry to check the lines and alignment.
• Sanding and shaving: Dial in the panel gaps so they are even across the car.
• Relieving stress: Using careful heat to help the material settle on tight curves or mounting points.

4. How to Spot Quality Before You Paint

Before you send your new kit to the spray shop, check these three things:

• Consistent thickness: Run your hand along the inner edges. It should feel even, not like a mountain range of resin.
• Crisp lines: Styling lines and body folds should be sharp, not soft, rounded or "washed out".
• The weight: It should feel rigid yet surprisingly light. Heavy and thick often means excess resin used to hide poor glass-work.

5. FRP Body Kit FAQs