The below will explain the codes on Nitto fittings; relying on Jacmark to correct me if I'm wrong (has been 20yrs since I sold them
)
The fittings will have a code stamped into them, example 20pm
20 = 1/4" bsp thread size or hose tail size
30 = 3/8" bsp thread size or hose tail size
40 = 1/2" bsp thread size or hose tail size
pm= Plug male thread
ph= Plug hose tail
pf = Plug female thread
sm = Socket male thread
sf = Socket female thread
sh = Socket hose tail
So for instance a 3/8" id air hose would be fitted with 1 x 30sh and 1 x 30ph, oh and two clamps of course.
So there's some almost useless info for u!