... envelope will rarely produce a result of thin film and mechanical standstill. - Film slitting good, with high-intensity endurance, ... Materials 27um, 29um, compared the cost of a cheap film envelopes 8% ~ 16%. 3. Spec. sizes of BOPS film : BOPS film (Biaxially oriented polystyrene film ... BOPS were most suitable use for the envelope window film thin, a very perfect read rates, can improve efficiency, ...