Size & colour guide

Plastic packer sizes & colours at a glance.

This guide shows how thickness, colour and typical uses line up across our plastic packers, so you can grab the right combination on site without guesswork.

Quick thickness & colour legend

Colours help you identify thicknesses quickly on site. Exact shades can vary slightly between batches, but the mapping below stays the same across our plastic packers.

1 mm — Green 2 mm — Black 3 mm — White 4 mm — Grey 5 mm — Blue 6 mm — Red

Plastic packers — size & colour

The table below covers the core plastic packers used across glazing, framing and general shimming. Widths are typically 20, 24 or 28 mm depending on the product.

Thickness (MM)	Colour	Typical use	Common widths (MM)	Notes
1	Green	Fine levelling, minor corrections and taking up very small gaps.	20 / 24 / 28	Use where you need minimal lift without changing sightlines or levels.
2	Black	Everyday packing, general levelling behind units and frames.	20 / 24 / 28	Often your first go-to thickness for standard glazing and frame work.
3	White	Slighter larger gaps, general squaring up of frames and sashes.	20 / 24 / 28	Useful for correcting frames that are slightly out of true.
4	Grey	Bigger tolerances and deeper gaps where 2–3 mm isn’t enough.	20 / 24 / 28	Often used in combination with 1–2 mm packers for fine tuning.
5	Blue	Heavier loads and deeper beds where more support is needed.	20 / 24 / 28	Use with caution; spreading load with multiple packers is preferred.
6	Red	Large gaps and heavy units where substantial build-up is required.	20 / 24 / 28	Combine with thinner packers rather than relying on a single thick piece.

How sizes & colours apply to other packers

The same colour/thickness logic carries through to different packer types, even though shapes and typical widths can vary by application.

Glazing Packers

Flat glazing packers support insulated glass units and glazed frames. They typically use 20–28 mm widths with 1–6 mm thicknesses to keep units level and square in the frame.

Frame Packers

Frame packers are designed for levelling and stabilising window and door frames, thresholds and similar elements. They often use a similar thickness range but in shapes suited to frame bearing points.

Specialist Packers

Specialist packers cover less common sizes, shapes or applications, such as wider bearing areas or specific gap requirements where standard glazing packers aren’t ideal.

Mixed Packs

Mixed packs provide a spread of thicknesses in one box, ideal for van stock and smaller teams who need flexibility on site without committing to cartons of each individual size.

Choosing the right packer

A few practical pointers to help you pick the right combination of width and thickness when you’re on site.

Match the width to the bearing surface. Use a packer that supports the area properly, not one that’s too narrow for the frame or unit.
Combine thicknesses. It’s better to use two or three thinner packers together than to force a single packer that doesn’t quite fit.
Spread the load. Position packers so that weight is distributed evenly, particularly under heavier units or frames.
Use the right type for the job. Flat packers under units, frame packers under sills and fixings, and specialist or mixed packs where profiles are unusual.

Good practice with plastic packers

Do

Check level and plumb before final fixing.
Use colour/size combinations you can repeat on similar installs.
Support frames and units close to corners and key load points.
Keep a consistent packer layout for easier future servicing.

Don’t

Rely on a single thick packer where several thinner ones would spread load better.
Pack only at the very corners and leave the mid-spans unsupported.
Mix random materials (wood offcuts, cardboard) with plastic packers.
Ignore visible twist, bow or racking after packing—adjust before you finish.

Size & colour FAQ

A few quick answers to common questions about packer sizes and colours. For more general questions, see the full FAQ page.

What thickness should I start with?

Many installers start with 2 mm (black) for general packing and adjust up or down as needed using 1 mm (green) or 3 mm (white) to fine-tune level and plumb.

Can I mix different thicknesses together?

Yes. Combining thicknesses is normal and often the best way to get the exact height you need without forcing a single packer into a gap.

Are these colour codes standard everywhere?

Colour conventions are widely used in the trade, but they aren’t legally standardised. Always check our product pages if you’re unsure about a specific line.

Do I need different packers for frames vs glazing?

Flat glazing packers are ideal under glass units, while frame packers or specialist shims are better under sills, thresholds and fixing points where loads differ.

Can I use plastic packers outdoors?

Most plastic packers are suitable for typical external glazing and framing conditions. Always follow the manufacturer’s guidance on temperature and exposure.

What if I’m still unsure which size to use?

Contact us with a photo or description of the job and we’ll help you choose a sensible starting combination.

Need more detail? Visit the full FAQ page.

Ready to choose your packers?

Use this guide as a reference, then browse the ranges below to order the packers you need.