Shore A is a scale from 0 to 100 that measures how hard solid rubber is – the higher the number, the harder. Most solid seals fall between about 50 and 80 Shore A: softer (50–60) for lips that must follow uneven surfaces, harder (70–80) for bases, channels and wedges that must hold their shape. Sponge seals are too soft for Shore A and are specified by density or by feel.
Typical hardness by part
| Part | Typical Shore A |
|---|---|
| Soft sealing lips, bulbs (solid) | about 50–60 |
| General gaskets, glazing | about 60–70 |
| Bases, channels, wedges | about 70–80 |
| Sponge / foam | Not Shore A – specify density or soft / medium / firm |
General guide values; your application decides the final hardness.
How it is measured
A durometer presses a small indenter into the rubber; the depth of indentation is read as a number. A tolerance of about ±5 Shore A is normal for extruded rubber.
How to state it
Write the target and tolerance, e.g. "60 ± 5 Shore A". If you do not know the value, send a sample or describe the job – we suggest a hardness for the application.
Need a seal for this?
Send your section, gap size or a photo of the old seal – Dora replies usually within 2 hours. Custom extruded & moulded rubber parts are available from 10 m.