CoolChange bicycle waterproof hard case rear bag. The bag has nylon netting separating compartments to hold all your valuables as in your phone, ear buds, keys, ect. The bag buckles under the back of the seat and straps to the seat post for stability and security. It is water resistant so you don"t have to worry about getting it wet in the rain. The material is a hard shell nylon with a PU pattern in the color black.