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Plastic Packers vs Plastic Shims: What Should You Search for and Buy?
If you are looking for plastic spacers for window, door, glazing, or frame installation work, you may see two terms used online: plastic packers and plastic shims.
In many cases, people use these terms to describe a similar job: filling a gap, levelling a frame, supporting a unit, or creating accurate spacing. But when it comes to buying the right product, the term you search for matters.
For glazing and window installation work in the UK, plastic packers or glazing packers are usually the more accurate search terms. If you search only for “plastic shims”, you may find a broader mix of products that are not always intended for glazing or frame installation.
What Are Plastic Packers?
Plastic packers are rigid plastic spacers used to create accurate gaps, support loads, level frames, and position components during installation.
In glazing and construction work, plastic packers are commonly used for:
- supporting sealed glass units
- levelling window frames
- aligning door frames
- spacing glazing units
- packing under frames
- correcting small installation gaps
- supporting joinery and construction work
The key benefit is consistency. A proper plastic packer has a known thickness, so installers can choose the exact size required for the job.
What Are Plastic Shims?
A shim is a general term for a thin piece of material used to adjust spacing or alignment. A shim can be made from plastic, metal, timber, or other materials.
So when someone searches for plastic shims, they may be looking for:
- glazing packers
- frame packers
- levelling shims
- construction spacers
- machinery shims
- furniture shims
- general-purpose plastic spacers
This is why the term “plastic shim” can be less specific than “plastic packer” or “glazing packer”.
If you are buying for window and door installation, it is usually better to search for the actual product type you need.
Are Plastic Packers and Plastic Shims the Same Thing?
Sometimes, yes — but not always.
In general conversation, an installer may call a packer a shim because both are used to create spacing or adjustment. But when buying online, the terms can lead to different products.
A plastic packer is usually a trade product intended for construction, glazing, frame alignment, and support work.
A plastic shim is a broader term that may include products not intended for glazing or building installation.
If you are fitting windows, doors, sealed units, or frames, you should usually search for:
- glazing packers
- flat glazing packers
- window packers
- frame packers
- plastic frame packers
- bridge packers
- wedge packers
Those terms are more likely to lead you to the correct trade product.
What Should You Search for If You Are Installing Windows?
If you are installing or repairing windows, search for glazing packers or window packers.
These terms are more relevant than “plastic shims” because they describe the products used to support and position glass units within the frame.
For window installation work, the main products to consider are:
Flat glazing packers are used for general support, spacing, and levelling.
Bridge packers are used where drainage and ventilation beneath the sealed unit need to be maintained.
Wedge packers are useful for fine adjustment and levelling.
What Should You Search for If You Are Buying for Glazing Work?
If you are buying specifically for sealed units, windows, doors, or curtain walling, search for glazing packers.
This is the clearest buying term for trade glazing work.
You can then narrow your search by size:
- 20mm glazing packers
- 24mm glazing packers
- 28mm glazing packers
- 9mm glazing packers
Or by type:
- flat glazing packers
- bridge glazing packers
- wedge glazing packers
This helps you find the correct product faster than searching for a general term like “plastic shims”.
What Should You Search for If You Are Installing Frames?
If you are levelling or aligning door and window frames, search for frame packers or plastic frame packers.
Frame packers are used for:
- door frame installation
- window frame installation
- levelling frames
- packing behind fixings
- keeping frames plumb and square
- construction and joinery work
If your job is more about the frame than the sealed glass unit, “frame packers” is usually a better term than “glazing packers”.
What Should You Buy for Window Glazing?
For window glazing, most installers should start with flat glazing packers.
At GlazingPacker, the main flat glazing packer widths to consider are:
The correct size depends on the glazing system and support area.
Use 20mm where a narrower flat packer is required.
Use 24mm as a versatile general-purpose option.
Use 28mm where a wider support surface is needed.
What Thickness Should You Buy?
The most useful thicknesses for many installers are:
- 3mm
- 4mm
- 5mm
These thicknesses cover a large share of everyday glazing and frame support work.
You should also keep:
- 1mm and 2mm for fine adjustment
- 6mm where available for larger gaps and stronger support
The best approach is to keep the common working thicknesses in bulk and use the smaller sizes for adjustment.
What Should Trade Buyers Keep in Stock?
For regular glazing work, a practical stock setup would include:
- 20mm flat glazing packers in common thicknesses
- 24mm flat glazing packers in 3mm, 4mm, and 5mm
- 28mm flat glazing packers in 3mm, 4mm, and 5mm
- bridge packers for suitable uPVC systems
- wedge packers for fine levelling and adjustment
- frame packers for frame installation work
This gives installers the right product for different jobs instead of relying on one generic “shim” for every situation.
Why Proper Plastic Packers Are Better Than Improvised Shims
Some installers still use timber offcuts, cardboard, or other improvised materials to fill gaps. That may seem convenient, but it can cause problems later.
Purpose-made plastic packers are better because they offer:
- consistent thickness
- cleaner support
- better long-term stability
- easier size identification
- resistance to moisture
- more professional installation practice
When installing windows, doors, or frames, the small saving from using an improvised shim is not worth the risk of movement, poor alignment, or callbacks.
Why Search Terms Matter When Buying Online
If you search for “plastic shims”, you may find a very broad range of products. Some may be suitable for construction, but others may be intended for completely different uses.
If you want products for glazing or frame installation, more precise search terms will usually give better results.
Use:
- glazing packers for sealed units and window glazing
- flat glazing packers for general glazing support
- window packers for window installation
- frame packers for frame levelling and fixing
- bridge packers for drainage and ventilation beneath sealed units
- wedge packers for fine adjustment
That way, you are more likely to buy the product that matches the job.
Common Buying Mistakes to Avoid
Avoid these mistakes when searching for plastic packers or shims:
- buying general-purpose plastic shims when you actually need glazing packers
- using frame packers where flat glazing packers are more suitable
- using flat packers where bridge packers are needed
- buying only one thickness for all jobs
- choosing the cheapest product without checking size and application
- using improvised timber or cardboard shims instead of proper plastic packers
The right product depends on the job, the frame, and the support requirement.
Simple Buying Guide
If you are not sure what to search for, use this simple guide:
- Search glazing packers if you are supporting glass or sealed units.
- Search window packers if you are fitting or adjusting windows.
- Search frame packers if you are levelling or fixing door and window frames.
- Search bridge packers if drainage and ventilation under the glass matter.
- Search wedge packers if you need fine adjustment.
- Search plastic shims only if you are looking for a broad general-purpose spacer.
For trade glazing work, “glazing packers” is usually the clearest and most useful buying term.
Final Thoughts
Plastic packers and plastic shims can describe similar spacing or levelling products, but they are not always the same thing when buying online.
If you are working on windows, doors, sealed units, or frame installation, it is usually better to search for the specific product you need:
- glazing packers
- window packers
- frame packers
- bridge packers
- wedge packers
For most glazing jobs, start with proper plastic glazing packers in the correct width and thickness. That will give you a more reliable result than buying generic plastic shims or using improvised materials.
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