Looks like some type of "mesh" fabric to me. It might have a specific name, I'm no expert. I'll add a photo here in case anyone else knows..
What do you call the "texture" of cloth used for Kylo Ren's armour? The stuff with "holes" in it? http://www.starwarsnewsnet.com/wp-content/uploads/2015/05/costume.jpg https://i.ytimg.com/vi/ps8WKlpOGgk/maxresdefault.jpg http://i.imgur.com/xktRi.jpg