Hearing aid mould types, materials and who they suit
The part of a hearing aid that sits inside your ear is called an ear mould. A custom mould is made to fit the unique shape of your ear with as much comfort as possible. Small vents in the mould let air pass through, so speech and the natural sounds around you still travel into the ear canal.
This guide explains the main mould types and materials. For impressions, fitting and prices, see the custom ear moulds service page.
Reviewed by Rose Multaney and Rauri Keogh, HearMed audiologists · Updated 10 September 2026
What a mould actually does
A mould holds the sound outlet in the right place and seals the canal enough to reduce feedback, the whistling that poorly fitted aids can produce. Moulds also give behind the ear (BTE) hearing aids extra reinforcement, keeping everything anchored comfortably.
A well-made custom mould improves the quality of sound you hear and helps reduce feedback and background noise. A poor fit does the opposite, which is why HearMed moulds are custom made from an impression of your ear rather than off the shelf.
Micro moulds
Micro moulds are custom made to fit snugly within the ear canal. They are the discreet option: an exact fit for comfort, improved sound quality and performance, virtually invisible when worn, and reduced feedback or whistling.
They suit people with narrow or sensitive ear canals who want the smallest custom option.
- Exact fit for best comfort
- Improved sound quality and performance
- Virtually invisible when worn
- Reduced feedback or whistling
- Suitable for narrow or sensitive ear canals
Flex moulds
Flex moulds are made from a softer, flexible material shaped to the exact contours of your ear. The soft fitting is comfortable over longer periods, very durable, and puts less pressure on ears that find harder materials uncomfortable.
They suit people with active lifestyles and anyone who wears moulds for long stretches of the day.
- Comfortable soft fitting
- Improved wearing experience over longer periods
- Very durable
- Less pressure or discomfort for sensitive ears
- Suitable for active lifestyles
Hard acrylic moulds
Hard acrylic is the traditional mould material. It offers exceptional durability and longevity, and it is easy to maintain and clean.
It suits people with energetic lifestyles who want maximum support and stability from the mould.
- Exceptional durability and longevity
- Easy maintenance and cleaning
- Maximum support and stability
Soft acrylic moulds
Soft acrylic gives a gentle, comfortable fit with enhanced flexibility. It suits sensitive ears or people prone to irritation, and it adapts well when the ear canal shape fluctuates.
It is a good match for prolonged wearing periods where comfort matters most.
- Gentle, comfortable fit
- Suitable for sensitive ears or people prone to irritation
- Enhanced flexibility and adaptability
- Ideal for prolonged wearing periods or a fluctuating ear canal shape
How we help you choose
The choice between micro and flex styles, or between hard and soft acrylic, comes down to your own preference, how sensitive your ears are, and your lifestyle. Our audiologists guide you through the selection in clinic and take the ear impressions the lab needs.
The same impression process also makes custom moulds for hearing protection, for example for musicians and motorsport, where a mould needs to stay put and carry the same filter every time.
Questions people actually ask
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