500 double window check envelopes self seal with security tint works with all software tech checks cut the time it takes you to pay bills with these envelopes - just stuff, seal and send. they're designed to be perfect companions to your qb checks. upper window 3 3/4 x 7/8 and 3/8 from left and 2 5/16 from bottom. lower window 3 3/4 x 15/16 and 3/4 from left and 11/16 from bottom