Looking at Z32 Brake Master Cylinders, what's the diffrence between 1" and 17/16"?

[Daemos]

I guess I should restate, and ask, what does that mean exactly?

Having a 1" master cylinder vs 17/16"? Is that just size? or Is it something else?

[C-Kwik]

A master cylinder with a larger piston diameter is going to move more fluid for a given piston travel. This means the brake pedal will feel firmer. The downside is that you have less leverage. But with a working brake booster, it won't be much of an issue with such a small difference.