Ball valve size

[frankrede]

thats a bbmg.
Which is good if you have access to a large size compressor.

[super spuder]

if you did want to make a bbmg you would probly use something like this if you could find it http://www.tylok.com/img/1mphc.jpg (the hose goes over the bumpy part and the threads go into the chamber) and then you would probly need a hose clamp to hold the hose on it. frankrede is right you would need a really big comressor to run one of those.