Most every blade we carry in sizes smaller than 12 inches will have an arbor hole size of either 1/2 inch or 5/8 inch.
These are the most standard arbor sizes on most wet saws. Many of our blades actually have both these arbor hole sizes on the blades. They will have a 5/8 inch arbor standard and will then have a small ring or bushing in the hole that reduces the arbor hole down to 1/2 inch. If you've ordered a blade like this and your saw has a 5/8 inch arbor on it. Simple look at the arbor hole on the saw blade. If there is a small ring there, just pop it out of the hole and your blade will now fit on your saw.
All of our blades 12 inches in diameter and over come with a standard 1 inch arbor hole.
None of our blade suppliers offer custom arbor holes any longer so if your saw requires something other than 1/2 inch, 5/8 inch or 1 inch, you might want to consider upgrading to a more modern wet saw.