Two Version , one with short nozzle (3) , One with long nozzle (4) ...to use with Atomstack Air assist pump or another air pump...the air is blown directly onto the engraving area, instead of from the supplied nozzle which causes burn marks from 50% power up even if light, with these air assist nozzles the cleaning of the cut is greatly improved...the original glass is removed and this is installed, quickly, only the small side allen is released....size suitable for the black tube supplied with the air assist atomstack