This is a chrome plated double nozzle used on the PFP (servo) cutting head on the some HTX, Mark III, and Optiplex lasers. This is the "Pencil" shape that is compatible with the nozzle adaptor part number M501S1 for the PFP (servo) cutting heads.
Double Nozzles have two chambers for the assist gas to flow through that changes the way the gas flows from the nozzle.
Chrome Plated nozzles are harder and last longer than the copper nozzles.
Also known as L1605X or 36143312311 or 36143312310.