#10 Security Self Seal Envelopes – 100 Qty |No Window, Enveguard, 4⅛ X 9½”, White, 24 LB, 100 Count (34100). EnveGuard Technology. our check envelopes are designed with an ultra strong SELF-SEAL adhesive strip to create a full, super secure seal across each envelope’s width that won’t easily open or tear.