SupremeX Outside Side Seam High Efficiency Envelopes - #10 - Window - 4-1/8" x 9-1/2" - 500 PackTrouble free insertion envelopes for high speed insertors. This envelope is made with wider and outside side seams which help prevent jamming when sheets are inserted. A security Artline provides added privacy for contents, meaning this envelope can be used for utility bills, credit card statements and more. It's also ideal for sending letters, memos, flyers and other correspondence.