The 1964-1966 Ford Mustang 7" Zinc Single Diaphragm Brake Booster requires 18" of vacuum to operate properly. With this vacuum level the booster will produce a maximum pressure output of 950 PSI with a 1" bore master cylinder. This pressure level will work great for four wheel drum systems and disc/drum vehicles which are relatively light.
**This booster is not recommended for heavy disc brake cars or any four wheel disc brake system.**