Weird material that has a squishy feel underfoot, but that's not the most annoying part of this rug. The color in the picture looks gray. The description says gray. There is nothing gray about this rug. I read some of the reviews saying it was green, but I thought "well, maybe its just a warmer gray that can have a tint of green". NO, this thing is olive green. no gray whatsoever. Sent back, only to have to pay about $10 in return shipping. Look elsewhere.