New Master Cylinder Part

Hello Guys!
I have a 1991 Acura Integra LS Hatchback. I’ve recently replaced all four brake rotors and pads. I’ve noticed over time before and after brake service, at a stop, my brake pedal goes all the way down to the floor. I’ve been looking on Rockauto.com for A-1 Cardone Master Cylinders. My question is, only the GS models has ABS and RS and LS don’t? Also I see bore differences with 15/16" (non-ABS?) or 1" (w/ ABS?).

You are correct. 1" = ABS ; 15/16" = non-ABS. GS and GSR models have ABS, all others do not.