turbotec

I just got a used turbo line from a guy, and I dont know what size AN the fittings are. I am assuming -4 but I dont want to buy the fittings and have them be the wrong size. I have that little AN to Thread size converter, but I dont know what size a 1/8 NPT is. I put my little 1/8 NPT male/Male fitting in there and it went right in, except for the fact that it wasnt compression fitting, if that gives you any idea of what size it is. any info would be awesome, and sorry for the dumb post