Active bolt for fire resistant doors designed to eliminate deformation of the point where it is installed, between leaf and frame, leaves and leaf and support. Single piece galvanised metal cylindrical body, machined from solid, dimensions 14x42 mm, fixing flange 25x3 mm. Conical metal sealing pin, variable diameter from 5 to 3 mm, length 17.5 mm, stroke 16 mm. Internal compression spring with 25 N thrust, operating temperature up to 540 °C, heating element to be installed if required. Weight of device, complete with strike: 51 grams. Heating element (to be installed if required) with ignition temperature of 110-150° C.