This is a picture of two non-adjustable AP Lockheed Front Master Cylinders.
The CP3179-2 (14-200001) is a 5/8" (15.875mm) cylinder and is to be used with a single disc system.
The CP3180-2 (14-200002) is a .7" (17.78mm) cylinder and is used with a dual disc system.
Both master cylinders fit a 7/8" handle bar.

We also have the above master cylinders in adjustable ratio versions.
The CP3125-4 has an effective bore size from 12mm to 16mm and is to be used with a single disc system.
The CP3125-2 has an effective bore size from 16mm to 19mm and is to be used with a dual disc system.