Remove the QD and take it with you to the hyd supply for a match. It is a National Pipe Thread Female, and 1/4 in size.
Since this is a quick coupler, and most of them do have female threads, JJ is probably right about being female. Still, I'd like to clear up a misconception that I encounter many, many times in my business.
The F in NPTF does not mean female.
NPTF stands for National Pipe Tapered Fuel. Both NPT and NPTF have the same threads-per-inch, pitch diameters, and taper-per-inch. The differences come in the major and minor diameters, the root and crest of the threads. The NPTF thread crests fall with in the parameters of the NPT requirements, but have a smaller range than the NPT.
ASSEMBLING NPT AND NPTF FITTINGS
NPT threads are designed to screw together. In most cases there will be no interference between the root and crest of the threads at assembly. The thread is designed to be assembled with some form of sealant to assure a leak free joint.
NPTF threads will screw together with NPT threads and should have no noticeable assembly problem. There will most likely be an interference fit between the root and crest on either the major or minor diameter of the thread, depending on which part is NPTF. To accomplish a seal on the joint, a sealant will be required.
NPTF threads are designed to screw together. They are designed to have interference at the roots and crests of the threads on both the major and minor diameters. This interference should cause no assembly problem. The thread deformation caused by the interference fit and the wrench tightening is designed to make a dry mechanical seal.
The requirements for NPT (National Pipe Thread) are spelled out in ANSI B1.20.1
The requirements for NPTF (National Pipe Thread Fuel) are spelled out in ANSI B1.20.3
