I would say that rubs on trees 6 inches or bigger usually indicates a large racked buck. A better way to tell is on groups of smaller trees bunched together. If the front is rubbed and there are marks on the back trees you can bet that the buck that did thathas an impressive rack. Also, if rubs are higher up on trees (4 feet plus) a big buck probably made that rub. All of these are indicators of rack size though. You really can't tell if a buck is mature or not from a rub.