gbreckley : The Space Needle is originally a 2C light with a rubber sleeve to choke the C barrel down to 123 size. You need 9V to drive it, or 3 123s. 123s are much cheaper now than a few months ago, but still relatively expensive.
Since the emitter is permanently attached to the 2C body, making a 4C extension provides a way to get the 9V using 6 C cells. This results in longer run time, but also a rather long light.
You need at least a 5C to make a 4C extension, since there's roughly a half a C cell's worth of inside threading on top to account for. I happened to have a Mag 6C, so I used that.
It was an exercise to learn inside threading.
ufokillerz : The 2C part is a real Space Needle.
Rothrandir : Email sent soon!
dw_1984 : Exactly right!