How do you determine it, i was looking up a nitrous fitting at work for a customer and how do you know if the fitting is 4 an 6an etc? Also the 1/4 and 1/8 on which side of the fitting are they taking that measurement because its two sizes on each end. As you can tell i dont know sh*t bout nitrous.

 

http://www.gre6.com/ansize
try that... i'm assuming that's what you mean

 

good enough, thanks man theo nly an fitting experience i got is on fuel gauges.