A 5500-06-06 | 3/8" NPTF Male x 3/8" NPTF Male 90° hydraulic adapter is a type of hydraulic fitting that connects two pipes or fittings with 3/8" National Pipe Taper Fuel (NPTF) male threads at a 90 degree angle. The NPTF thread is a type of tapered thread used for pipes and fittings in hydraulic and pneumatic systems. The thread design provides a seal between the male and female threads that increases as the threads are tightened. The 90 degree angle of this adapter allows pipes or fittings to be connected at a right angle, which can be useful for routing hydraulic lines in tight spaces or for making turns in a system.