Grease fitting on A arm

What size is the thread on those little fellows? I know it's smaller than a 1/8" pipe thread..

The top one on my upper A arm twisted out when I was taking the grease gun off after greasing it..
The metal is very thin and cannot have but one or two threads,I got it back in, but it now leaks grease out around the fitting when I apply pressure with the gun..

I don't know hank , I never had one of them out....

Chris after looking futher into the situation,without changing the A arm,or taking it apart.. I'm going to tap out a thicker piece of metal,and not wanting to weld on the A arm tube, I'm going to clean it good and JB weld it on the A arm tube over the grease fitting hole and install a new fitting,may use the 1/8" zerk if I cannot find a smaller pipe tap..Just saying..

I may be wrong, but I believe it is a 1/4 - 28 bolt thread...that or a metric thread 6mm or possibly 8mm

The same thing happened to me, but it was the rear lower that broke off. I have never repaired it. I had just got the machine running after the frame change and said screw it. When it starts to make a racket I will just re-bush with the greasless ones from RacerTech. Should have done that during the frame job, but ran out of money.