Temperature sensor for liquid cooled Minarelli engines.
The long one is used as a switch for Aerox with just a temperature light.
The short one is a thermistor (for Aerox with a temperature gauge) and is a genuine Yamaha part.

A "switch" sensor simply switches on and off at a certain temperature and normally operates a warning light on the dash.
A "thermistor" sensor changes resistance at different temperatures which means it can control a temperature gauge to display the actual water temperature.

Thread:
Short sensor M10x1.0mm
Long sensor M10x1/8

5BRH360501, 5BSH360500