The grey tiles are stone-like and, according to the store display, eco-friendly. I haven’t done the research to find out why or how they merit their green label. They were on sale and to be discontinued, so we ended up with several free boxes that will soon be used in the kitchen. The big white subway tiles for the children’s shower were in the closeout room and way more economical (and fun) than the smaller size we had intended to use. Chris has done all the tile work himself, a first-time experience with this craft.