For Rancilio Silvia coffee machines, this is a water level indicator to alert you when the drip tray is full or nearly full.

It is designed to remain attached to the drip tray cover but can be easily removed as needed.

The duct is designed to be pushed tightly into any of the holes on a Rancilio Silvia drip tray cover. Avoid the first row so you leave enough room for the float not to hit the side.

The float is largely hollow to ensure it actually floats.