P C Henderson Ltd’s Marathon Fire Door Kit is solely designed for use with Marathon S3, S4, S5 or S6 gear kits, these fire door kits are produced in one standard size weighing up to the maximum of 90kgs. Marathon Fire Door Kit is a system developed as part of a half hour sliding fire door assembly to BS 476: Part 22: 1987, and should be installed on the non-fire risk side of an aperture.