Astro ASDB/SM Seal - Acoustic Rated Door Bottom Seal - Surface Mounted Fire doors with a gap of 5mm or more at the bottom require a threshold seal to maintain integrity. I have 3 sizes available 730mm, 830mm and 930mm. If you require multiple items contact me directly for best prices. The surface mounted drop down smoke seals offer a quick and easy solution to preventing smoke, draughts and even sound from passing through the gap at the bottom of a fire door. Suitable for gaps of up to 14mm, these seals are ideal for retrofitting as they require no routing or rebating. When the door is closed a plunger makes contact with the door frame and lowers the PVC rubber pad in the bottom of the unit, effectively sealing the gap under the door. Surface mounted drop down threshold seal Suitable for push or pull side installation Graduated scissor action – seal drops on hinge side before lock side Available in a range of lengths: 730mm/830mm & 930mm Lightweight satin anodised aluminium construction Insulates against smoke, draughts and even sound Ideal for retrofitting existing fire doors Suitable for use with surface mounted fire door seals Easily trimmed to fit any door (maximum trimming length 150mm) Supplied complete with fixing screws Maximum drop: 14mm Please note: This seal operates via a graduated scissor action, meaning that the seal drops on the hinge side before the lock side. Once installed correctly the entire length of the seal will drop when the door is fully closed. The Astro ASDB/SM Seal is a high-quality, surface-mounted door bottom seal designed by Astroflame. Made in the United Kingdom, this silver anodised seal is perfect for ensuring a secure and acoustic seal on your door. With its sleek design and durable construction, this product is a reliable choice for keeping out noise and maintaining a comfortable environment in your home or office.