The brake master cylinder is a replacement part for Wilwood# 260-8555BK. The piston diameter of this one is 1″ (equal to 25.4mm). It is black painted type. The two outlet ports are on left side which is 9/16-18″ & 1/2-20″. And for our HBS part number, it is AU0501-MC002. We also have 1-1/8″ bore diameter brake master cylinder ( replace Wilwood# 260-8559-BK). Our MC002 black anodized aluminum manual master cylinder fits for 1964-1973 Mustang.