Standard mini pressurestat fits numerous prosumer machines such as the ECM Giotto, older model Rocket Giotto and others.
Pressurestats control the pressure (and by extension) the temperature of your espresso machine boiler. This mini pressurestat has an adjusting screw to vary the boiler pressure within acceptable limits (usually set to 1 to 1.2 bar). Rated for both 110-120V and 220-250V.
These mini pressurestats are used on most prosumer machines ( check to see if yours uses the 1/4 (more common) or 1/8 (less common) threads. The center spade (NO - normally open) on the microswitch is not used.