I recall when the CDMA iPhone came out the old bumpers would not fit due to slight movement of the volume buttons. Apple now sells a universal bumper? Was the design actually changed? Or do all bumpers ever fit all iPhones? I would like to order a new grey bumper off Ebay for the upcoming white 4S, but some say "AT&T or Verizon only" and im not sure of the exact external changes. Appreciate any info.