This is an air nozzle to direct air onto freshly extruded layer of print . For v6 style extruders with square heat sink for feed such as Tevo Tarantula . May work on other extruders with 30mm cooling fans . The fan that you will need to get for use with this nozzle is a 40 mm fan.
A video is available to explain the assembly and use on you tube .
The Gcode is for those who have the usual .4mm extruder nozzle.
One thing , Clearances are tight , so just make sure the extruder nozzle is lower than the bottom of the gunnozzle so as not to bottom out the gunnozzle against the bed . For fan , use #4 x 5/8" pan head sheet metal screws.
The Gunnozzle should attach to the heatsink & fan with original screws . At least , they do on the Tevo Tarantula .