Thread: How do you measure NPT fittings???

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....Thanks!!! ... a couple more pic's. The fitting on the left is the same fitting that I have in my first pic. So by reading my replys I'm thinking that the fitting on the left is an 3/8" NPT with washer {because the threads aren't tappered} & the fitting on the right is an 3/8" NPT w/ out washers because it's tappered.... Oh, fitting on the left is one of the two fittings that comes out of my turbo 400 transmission that goes to the transmission cooler. Fitting on the right is one of two fittings that goes into my transmission cooler.... One more question. I'm assuming the answer is yes but; Are the female threads the same for the NPT with & without washer? Meaning can I use 3/8" NPT tappered fittings in both the transmisson & the trans cooler? I hope I'm making sense! THANKS again!!! Bill