When the GSR750 was replaced by the GSX-S750 in 2017 one of the major upgrades was the braking system, the Tokico Twin pot calipers were replaced by Nissin Radial 4 pot calipers and standard ABS.
However the master cylinder stayed as an Axial 14mm master, this gave teh 750 a very long soft brake lever. I upgraded the stock Master cylinder on my 1000F to a Brembo RCS so we decided to upgrade my friends GSX-S750 with the master cylinder off the 1000F.
The 1000F has a Nissin 19mm (3/4 inch) Radial Master Cylinder. The 19mm has almost double the area of the stock 750 14mm cylinder reducing the travel of the lever considerably, Being radial gives slightly more rigidity and feel too. Huge improvement to the braking.