Pneumatic soda can cannon on Mythbusters?

I just watched a Mythbusters where they made a pneumatic soda can gun.  Go to 5:50 in this video to see their description of it.  Go to 7:00 to see it in action.  

http://www.youtube.com/watch?v=ZMYuQ5daXxk&feature=related


My questions are:
what is the "fast acting valve" he used?  
How do you refill that thing?
Anyone seen an instructable for something similar?  I've seen lots of PVC versions, but I like the metal version because it's sexier looking, and potentially higher pressure/power.

Thanks!