Gelugpa "Yellow Hat" Question

I'm writing on Tibetan Buddhism for a project, and despite my research I can't figure out what the name for the hat featured in this image is. What is the name of the hat that those in the Gelugpa school wear? All I've run across is "Yellow Hat". https://c1.staticflickr.com/6/5328/8976045398_6dc337e954_b.jpg