A1 Envelopes - Twilight Blue - 3 5/8 x 5 1/8 (for response cards) (pack of 250) Envelope Size: 3 5/8" x 5 1/8" Fits Card Sized: 3 1/2" x 5" 60lb paper weight (standard envelopes) Square Flap (gummed) pretty, twilight blue