The Tred Zip Folio is a slim and highly protective work-in case solution. Its tension clip system adapts to different device screen sizes and keeps devices firmly in place within the case at all times, while the sturdy edge of the case extends beyond the device to create a shock absorbing crumple zones. HDF™ Protection System The Brenthaven patent-pending HDF™ Protection System uses a lightweight cradle system and a layer of high density foam to create both physical distance and protective padding between the device and the exterior of the bag or case, minimizing device vulnerability in the event of a drop.