I'm fairly sure as the original won't fit on anything I have and they are Schon and Schrager cues, which are 5/16x14 I believe. I called Russ a few years back and he said he used a different thread size early on.
I tried my OB1 shaft on JoeA s cue it did not fit and that shaft (5/16 14) fits every cue I have with that pin.I think his Espirtu is a 5/16. 18.The best thing probably is to call the cue maker.