This valve top fits onto a Schrader valve to form a top similar to what is found on top of an Aerosol air duster, with the exception that this air duster can be easily refilled with a normal bicycle/car tyre pump.
This this youtube video I discuss how the model was designed, printed and used: http://youtu.be/pmN559MlUPg
I specifically designed this part to print without the need for any support material as you would not be able to extract the support material after the part was printed anyway. It printed fine on my custom single extruder Delta 3D printer.
Watch my Youtube video for a full description of how the model is designed, printed and used.