Abstract: The window material is made of two layers of material that have different elongation properties. The layers are bonded together to produce a multi-layer laminate that has sufficient optical clarity to easily read or scan the printed matter on the I.V. bag, has sufficient flexibility to provide maximum contact with the I.V. bag, but has little or no stretch to provide uniform pressure on the I.V. bag at typical utilization pressures. The preferred embodiment is a 10 mil, matte finished, high Durometer polyurethane film laminated to a 92 gauge (0.00092?) polyester film.