ROCKWOOL FLEXI® has been designed as a multi-use, dual purpose acoustic and thermal mineral wool insulation with a unique flexible edge along one side. The FLEXI slab is manufactured with the patented flexible edge which ensures a perfect fit is maintained between the insulation and the supporting framework. The insulation can be fitted between fresh timber and will expand into the wider space as the timber dries out and shrinks back. Other types of insulation can often become displaced resulting in cold spots or poor acoustics. FLEXI provides excellent thermal and acoustic performance as well as being A1 classified non-combustible for fire resistance.

https://www.insulationbee.co.uk/50mm-rockwool-flexi-slab-multi-use-...

ROCKWOOL FLEXI® is easy to install and has optimum effectiveness. It is suitable for use all over the home, in pitched roof rafters, framed external walls, internal partitions, intermediate floors, separating walls and floors, and timber suspended ground floors.
Description
ROCKWOOL FLEXI® is a multi-use, thermal, acoustic and fire insulation product with a unique flexible edge along one side. The patented flexible edge ensures a perfect fit is maintained between the product and its supporting framework for easy installation and optimum effectiveness. FLEXI® is suitable for use between frames in walls, partitions, floors and roofs, without the need for cutting or waste. Made from renewable volcanic rock, it is extremely fire resistant and significantly reduces the carbon footprint of a building.