They're called that because they are ideal for surveillance activities. The outer edges of the inside of the lens are coated with a silver-like substance which reflects what's going on behind you on either side. Even the lens are angled in such a way that they facilitate seeing clearly behind you. Large numbers of these glasses have been sold to cycling clubs as an ideal way of watching the traffic without having to rubberneck. Once again, ideal for Private Dicks and ... er, really paranoid people. Available at an RRP of AUS$45 from ozspy.com.au