Special tools are required

Familiar with Ducati and Gucci from the air-cooled era.
This is a replacement piston for bremboSmall diameter MASTER PS12 from the round body era.
Gucci FMASTER of 350~650 PANTAH and Integra Le Braque era is Large body.
It is also used by some Rear master of the same age group.

Originally, the replacement parts for Black Anodized Aluminum round bodies were iron pistons,
Thankfully, since the 1990s, for Race (GoldAnodized) The aluminum piston has been integrated into the same anodized aluminum piston as the
As with the MASTERBody, the aluminum material makes the inner walls of the cylinder less susceptible to potentiometric corrosion than iron pistons.
If the Cylinder is so corroded that you can feel it with your fingertips when you close it, it is Out.
Aha, MASTER-kun, who is poorly maintained, is going to the scrap bin.

The brembos of this era used a deformed washer instead of a SurfClip to fix the position of the piston.
Pin punch of appropriate length for removing and installing the piston, and a special installation tool for inserting a new piston. (Discontinued) is required
The fact that you need a special tool means … I'm sorry if you bought a used car from a non-specialist store.
The 40 year old iron Piston is untouched and in place.
In rare cases, there are people who use a hollow pipe for installation without special tools.
The thin part of the lever holder is always scratched.

Specialized tools can be found in a store that specializes in ita-vehicles of this era.
So if you don't have special tools, ask a store. It is worth the labor cost. View detail

It seems to be the same spec. that has remained unchanged for many years.

Used for a Master Cylinder with an integrated horizontal tank, which was adopted by OEM for a very old DUCATI.
It was Master Cylinder in the 70's, but I am surprised that Piston is still commonly available & continues to be used in the current Master Cylinder.
As for Seal and Piston, I am impressed that they were very well designed. View detail