The Element Case Atom S4 offers a semi-flexible chassis made of impact resistant TPU that is soft to the touch, yet extremely tough. The Atom S4 also incorporates the new proprietary SBS (Sound Boost System) that channels sound waves from the rear facing speaker and directs them to the front of the case, while amplifying the levels. The ultra slim Atom S4 utilizes a genuine carbon fiber protective back plate for added protection and rigidity. The sleek, ergonomic design, SBS, carbon fiber, and polycarbonate reinforced corners makes the new Atom S4 a premium case at a terrific price.