6x9 Tyvek sub 14. Open End envelopes Zip and stick on flap. Brand new box of 500 envelopes. Tyvek is a brand of synthetic flashspun high-density polyethylene fibers. The name Tyvek is a registered trademark of the American multinational chemical company DuPont, which discovered and commercialized Tyvek in the late 1950s and early 1960s. This makes the envelopes very durable. Thanks for checking my item.
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