[RichardJ]

Master with deep hole is for manual brakes and uses the dust boot.

CPP sells a master with deep hole and provide a spacer plug so that it can be used with a power booster. If you know what you are doing and have a lathe, you can make your own spacer. If not, return it for the correct master.

No matter what you do, the adjustable pin in the booster must be checked and adjusted to fit the master.