Threaded spin-on for gearbox and compressor lube circuits.
A 10 micron spin-on with an anti-drainback valve and a 25 psid bypass. The common size for small gearbox and rotary-screw compressor lube circuits. Check the thread before ordering; 1 in-12 and 1-1/2 in-16 look alike in a parts bin and do not interchange.