The Issue, Continued... The blue Tee connector shown has a 3/8 NPT thread on the upper leg. it is a 3/8 x 24 National Pipe Thread. That is, it has a tapered thread. The thread measures 0.373 in on the narrow end and 0.408 in on the wide end. The other fitting was removed from the brake. It is a 3/8 x 24 straight thread, 0.391 in d. No taper. That's why the AN fitting will only screw in about 2 threads.