Heated Eyepiece Cup
 

Just wondering why someone would go heated vs non heated.

Prevents fogging and condensation on the diopter lens when you put a warm body against it.

It's a luxury option :)

It's pretty much necessary in order to operate the camera across many different environments on location. From mountain and snow work right down to jungle work... if you don't have a heated eyepiece to prevent condensation, you will struggle with operating.