What is a Fitter Hole?
A complete guide to understanding fitter hole sizes, vase caps and how to measure your glass shade correctly.
When replacing a glass light shade, one of the most important measurements is the fitter hole. This is the centre opening in the shade that allows it to fit onto a vase cap or spring clip fitting.
Measuring this correctly is essential. If the fitter hole is the wrong size, the shade may not sit securely, may not fit the vase cap, or may become unstable once fitted.
What is a Fitter Hole?
The fitter hole is the opening in the centre of a glass shade. It is measured straight across the opening in millimetres.
Why is the Fitter Hole Important?
Even if two shades look similar, they may not fit the same light fitting if the fitter hole sizes are different. A difference of just a few millimetres can prevent the vase cap or spring clip fitting from holding the shade correctly.
This is why the fitter hole should always be checked before ordering a replacement glass shade.
Step 1 – Remove the Shade
Carefully remove the glass shade from the fitting before measuring. Place it on a soft surface to avoid chips or scratches.
Step 2 – Measure Across the Opening
Measure straight across the widest part of the centre opening using a ruler or vernier caliper.
Do not measure the overall shade width. Measure the centre hole only.
Step 3 – Record the Measurement
Record the fitter hole size in millimetres. This measurement is used to match the shade to the correct vase cap or spring clip fitting.
Example: 57mm fitter hole
Common Fitter Hole Sizes
Some of the most common fitter hole sizes include:
- 30mm
- 40mm
- 57mm
- 80mm
- 100mm
Always measure your existing shade before ordering, as sizes can vary between traditional, antique and modern fittings.
Fitter Hole vs Shade Diameter
The fitter hole and the overall shade diameter are two completely different measurements.
The fitter hole is the centre opening in the shade. The shade diameter is the widest part of the glass shade.
Example: A shade may have a 150mm overall diameter but a 57mm fitter hole.
What is a Vase Cap?
A vase cap is a metal fitting that sits on top of the glass shade and secures it in position. It is commonly used on pendant lights, ceiling lights and traditional glass shades.
The vase cap must suit the fitter hole size of the shade. If the size is wrong, the shade may not sit correctly or may be unstable.
Common Measuring Mistakes
- Measuring the widest part of the shade instead of the centre hole
- Measuring at an angle
- Guessing the size instead of measuring accurately
- Measuring while the shade is still fitted
- Rounding the measurement up or down
Can I Use a Different Size?
The fitter hole should match the fitting as closely as possible. Using the wrong size can cause the shade to sit incorrectly, move around or become unstable.
Need Help Choosing the Right Size?
If you are unsure which fitter hole size you need, simply send us:
- A photograph of your light fitting
- A photograph of the glass shade
- The fitter hole measurement, if known
- The overall shade diameter, if known
Our experienced team can help identify the correct fitting or replacement shade.
Frequently Asked Questions
Is the fitter hole measured in millimetres?
Yes. Fitter hole sizes are normally measured in millimetres.
Is a fitter hole the same as a fitter neck?
No. A fitter hole is a centre opening in the shade. A fitter neck is a raised neck around the opening, usually used with a gallery.
What are common fitter hole sizes?
Common fitter hole sizes include 30mm, 40mm, 57mm, 80mm and 100mm.
Can I make a fitter hole larger?
No. Glass should not be drilled or enlarged after manufacture, as it is likely to crack or break.
Can John Moncrieff help identify my shade?
Yes. Send us photographs and measurements, and we will help identify the correct replacement where possible.
Need Advice?
John Moncrieff supplies a wide range of replacement glass shades and lighting components. If you are unsure which fitter hole size you need, our team will be happy to help.