Our “Slim-Jim” Window

The ultimate Slimline uPVC Window

Exclusive to Firmseal

Less frame, more light

The elegant, slim framework of our exclusive Slim Jim uPVC window system allows more light to flood into your home.

The ultra slim sightlines provide a much greater glass area than current standard casement windows and are perfectly suited to both modern and traditional houses.

Beautifully refined ultra slim sightlines

Our exclusive Slim Jim window system is defined by its stunning ultra slim sightlines. Slender and elegant, they allow for a greater glass area and give a more refined look to a property – whether it is of traditional or contemporary design.

More glass means much more light

The increased glass area of our Slim Jim windows allows your room to be flooded with significantly more natural light, creating a warm and airy home environment for you and your family.

You’ll be amazed by the difference that the Silhouette’s slimmer frames can make to the ambience of your home.

Available to view at our showroom Download brochure

The Firmseal process

We pride ourselves on offering the very best experience for our customers throughout every stage of the process.
Known fondly as the “Firmseal experience".

From quote to installation, we make it easy for you!

"We had dealt with Firmseal in the past. Came over and looked at showroom, was impressed, staff so helpful, everything went smoothly from start to finish. So nice to get to speak to a person at the end of the phone. Thank you to everyone."

Mrs M – Windows, Yeovil








What our customers say

Don’t just take our word for it. Hear what our customers have to say!

Excellent product & better value for money than competitor brands. Customer service has also been very impressive. We love our new windows.

Mr & Mrs T

Alitherm, Yeovil

Completely satisfied, you came recommended by my sister who has had various work done by yourselves.

Mrs C

Back Door, Yeovil