"What is the standard collar size for predator shafts?"
That in itself is somewhat of a misleading question in the sense that Predator doesn't make a 'one size fits all' shaft with regards to joint diameter. Collar size, as you call it, for factory finished shafts is determined by the pin that you have in the handle.
Finished Predator shafts from the factory have fixed parameters for each pin so each pin will have a different collar diameter for the shaft.
For example:
18 thd.= .830/.835"
14 thd.= .840/.842"
10 thd.= .850"
Radial = .850"
UniLoc = .845"
These are the std. diameters for the vast majority of 'production' cues. If the cue you are inquiring about is a custom then joint diameter is at the discretion of the builder. Since you haven't received the cue yet, you may be putting the cart in front of the horse, so to speak. Once your cue arrives you'll be able to take the necessary measurements to make your decision. When ordering any shaft you'll want to know, A.) what pin you have. B.) collar/joint diameter. C.) deco-ring configuration.
Even if your cue falls outside of the 'fixed parameters' for factory finished shafts, all of the performance shaft manufacturers offer what is known as a 'partial' shaft (unfinished at the joint end), that you can have custom fitted to your cue by a CM of your choice. Seybert's offers this service and in most cases is a 3 to 4 day turn-around. Hope this helps.
