The most famous products of Cross-Line is its ultra-thin metal bumper case for iPhone 4/4s. SP-4 Series is one of the lightweight metal aluminum cases for Apple iPhone. A simple bumper case, we know, does not offer a whole lot of protection but much better than a naked phone. It can keep your phone away from scratches and dirts, protecting the frame & cutouts of a phone. If you are the man who go for uber-cool bumper case, this SP-4 Series crossline iphone 4s iphone 4 metal bumper case is made for you, as its .7MM of the thickness.Check it out!