CellPowerCasesTM Keep Calm Knit On iPhone 4 Case - Fits iPhone 4 & iPhone 4S 30 Day Satisfaction Guarantee. Cases are produced in and ship from the United States with USPS Tracking provided. This lightweight and durable custom case allows easy access to all sensors, ports, and controls on your phone, regardless of your service provider. This case is made of hard silicon, offering solid protection without adding a lot of bulk. The printing methodology used is sublimation, which offers a bright and durable print on an aluminum backing.