(continued)... reduced protection should fire occur. These covers are inexpensive and install quickly with no need for drilling or screws. Constructed of fire-resistant char, the covers expand in extreme heat providing a full 60 minutes of fire resistance. Also acts as an insulator, reducing the likelihood of ceiling dust and insulation ignition. An appropriate choice for suspended, concrete and plasterboard ceilings. Your choice of five sizes ranging from 150mm x 150mm up to 350mm x 230mm. Covers meet all requirements for NHBC type approval.