About Intumescent Liner for Letterbox Openings in Doors
An intumescent liner comprising two L-shaped sections fitted with self-adhesive backing for ease of fixing. The liner can be cut to size with a sharp knife to fit the opening. Sizes to suit other openings can be made to order. It is used for mail apertures in fire doors, where existing letter flaps are to be used.
Standard opening sizes are 65mm x 290mm and 85mm x 340mm