This revolutionary retro fit seal increases acoustic performance of a standard fire rated door simply and effectively. Its design is based on ‘dual air pocked technology‘ which acts in the same way as triple glazing. The NOR710 also has smoke seal capabilities in accordance with BS 476 Part 31:1 and is unaffected by door furniture including hinges and latches. We have cycle tested the NOR710 acoustic door seal up to 100,000 opening and closing cycles. CF 629
 

The recommended gap tolerance is 3mm - 4mm.