OEM 54308301 M630174 master cylinder brakes is 25.4mm (equal to 1 inch) bore diameter. There are two outlet connectors which thread measurement is M12. It fits for Mercedes Benz Trucks E-class(E320, E430) T-modell S210 E200 and so on. The master cylinder is made by aluminum material.The rubber components are made by EPDM, which is hightly resistance to glycol-based brake fluid.