What sensor is next to the water temp sensor?

Hi guys.
My temp gauge is dead and I had a look under the bonnet. The clip has broken off the top of the sensor next to the water temp sensor. So what is this sensor?

I need to get a new one but I can't figure out what itnis called.

Cheers.

 

One sensor is for your gauge, other for the ECU.

 

Yep, little one is for your gauge. Big one for the ECU.

 

Thanks guys.