500#10 Security Self Seal Envelopes, Windowless, Premium Security Tint Pattern, Ultra Strong Quick Seal Closure, EnveGuard, Size 4-1/8 x 9-1/2″, White, 24LB, 500 Count(34010). 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.