Sturdi-Kleer Vinyl Envelopes are made of a heavy, crystal clear vinyl and thumb cut fronts with exclusive patented flaps at the openings that fold over to protect contents from dirt, moisture and from falling out. The heavy, crystal-clear polished vinyl will not yellow or crack with age. The exterior has a smooth, double electro-weld edge that is reinforced at the maximum stress points. Sturdi-Kleer Envelopes are available in packs of 10 in a variety of sizes. Advantus Corp. is dedicated to providing innovative quality products at fair prices.