Expansion Valves for most Rancilio Espresso Machines.
Technicians Tip: If water is dripping into your drip tray from a small copper pipe (or silicone pipe, Classe 7,9,10, 11) during normal operation, it means the expansion valve is worn and must be replaced. Note: All machines will drip initially during the start-up phase and is normal (that's the expansion valve working).
The Metric "1/4" thread is actually about 1/2 inch across and the Metric "3/8" is actually about 5/8 inch across for reference purposes.
Part # RA_10.060.460.