The Portwest B121 Thermal Trousers are a base layer for keeping your legs and lower body warm in cold conditions. They are designed to be worn next to the skin, beneath your usual work trousers.
The soft polyester and cotton fibres and the knitted construction hold a layer of warm air around the body. An elasticated waist and a ribbed, cuffed hem keep the trousers in place as you move.
Key features
- Knitted polyester and cotton fabric traps heat close to the body for insulation
- Soft fibres for wearing next to the skin
- Elasticated waist holds the trousers securely in place
- Ribbed cuffed hem helps keep warmth in at the ankles and stops the legs riding up
Materials and performance
50% polyester, 50% cotton, 200g.
Standards and protection
Certified to EN 14058 Class 2 for protection against cool environments, with a thermal resistance of 0.137 m².K/W and a Clo value of 0.9.
Fit and sizing
Regular fit. See our Portwest Sizing Guide for detailed information.
Layering
Wear them as the first layer under your work trousers or waterproof overtrousers. The cuffed hem sits neatly inside socks and boots, so the outer layer goes on easily over the top.
Care
- Machine wash at 40°C on a gentle cycle
- Do not bleach
- Do not tumble dry
- Line dry
- Iron at a medium temperature (max 150°C)
- Do not dry clean
Add your logo
If you’d like to add your logo to the Portwest B121 Thermal Trousers, please contact us.

























