Kriega Back ProtectorThe ultra lightweight Kriega Back Protector fits neatly into Kriega backpacks, delivering the highest level of CE-approved impact protection. Designed as a fit and forget insert, it shields your back regardless of what youre wearing underneath.Features: RHEON RHEON technology is an energy-absorbing super polymer. It is soft and flexible in its natural state but absorbs energy by stiffening when subjected to force.In helmets, RHEON is crafted into a "metamaterial" using carefully developed geometry combined with the active polymer to reduce the forces transferred to the brain.The unique anisotropic shape allows the cells to absorb energy differently in compression and shear. The adaptive chemistry of RHEON maximizes absorption of low-speed linear and rotational impact energy depending on the severity and direction of an impact. patented algorithmic design mimics how cells are packed in nature which helps materials to be naturally lighter Dynamic, reactive material gives impact protection exactly where its needed, while maintaining total comfort and flexibility Compatible with all KRIEGA backpacks besides the Hydro-2 hydration pack Dimensions:15.9 x 6.1 x 0.7 inch