Heavyweight Clasp Envelopes are an excellent solution for accessible storage or filing, making staying organized easier. Use for projects, filing and mailing. Heavy-duty, double-prong clasp and reinforced eyelets are durable for repeated use. Envelopes are made of 28 lb. brown Kraft stock that withstands extensive handling as well as mailing. Contents are protected during use to give you assurance that it arrives unharmed. When folding is undesired, these envelopes are the right choice. Heavy gumming keeps envelopes securely and permanently sealed when needed.