Acer Chromebook 311/C721 Case Gumdrop's DropTech Acer Chromebook 311/C721 Case is a shock-resistant combination of TPU rubber and rigid polycarbonate casing for Acer's newest Chromebook. The case features asset tag and embellishment friendly top and bottom and lightweight, 2-piece construction that is simple to install onto the device. Dual material construction (PC & TPU) allows for easy asset management and prevents sliding on desk and countertops. The case is charge cart friendly and Prop65 compliant.