The glass bulb is about 15mm long (about 5/8").  These were once commonly used as power indicator lights, and are still in wide use.  I have 11 of these that I put into the glass salad dressing jar, same as was used for the green glass lamp experiment.  About 150 mL of water was added to the jar.  The water gives the microwave oven a 'load' (a place for the energy to go).  It also keeps the NE2 lamps from melting. 

This test can be conducted for a longer period of time (30 seconds?) and should be stable as long as the water doesn't boil too much.