Blue Summit 100 Tyvek Envelopes 10X13, Large 10X13 Envelopes Self Seal, White Tyvek with Center Seam. Material Tyvek. Material Type Tyvek. Manufacturer Blue Summit Supplies. Our 10″ x 13″ Peel and Seal envelopes easily create a strong seal so your contents are will stay inside the envelope without the need for glue sticks or tape.