This is used to connect the pressure washer spray gun to the wand / lance. Often people would come into our shop and ask us to put the fitting on the actual spray gun so they can use it without a wand or they can simply attach different lengths of wands to the gun.
The male pipe thread will screw into the spray gun. The quick connect coupler will allow you to connect attachments, wands and accessories to the gun.
Note* always use teflon / thread seal tape when installing into gun and be sure to install a new o - ring in coupler end.