The front and back cover is made out of 100 % Carbon Fiber Plates with magnets to securely close each side of the pad that forms a slot for a metal twist magnetic pen. When inserted into the slot the pen holds the notebook covers together, effectively locking it. Paper sheets are waterproof and the entire set of pads is replaceable, in either plain or grid pattern. Made from engineered paper, stronger and durable for all weather conditions. Parts & Features: 100 % Carbon Fiber covers. 100 % Waterproof composite paper (50 sheets). Magnetically Secured with Neodymium Magnets. Mini EDC metal twist pen77 mm wide x 130 mm long. Replacement notepad sheets are available.