Most audio components have standard physical dimensions, but televisions vary widely in height, width and depth. If a customer's television is too deep for the entertainment center, its back will protrude beyond the back of the case and force replacement of the case away from the wall. If a TV's width and height exceeds the physical dimensions of the case, the television will not fit at all. Television tube size is measured diagonally across the front of the tube. Today's sets generally have similar dimensions, but older sets vary widely in height width and depth. Larger tubes are becoming more popular.