A1 Envelopes - Light Gray 70lb - 3 5/8 x 5 1/8 (for response cards) (pack of 100) Envelope Size: 3 5/8" x 5 1/8" Fits Card Sized: 3 1/2" x 5" 70lb paper weight (slightly heavier than standard envelopes) Square Flap (gummed)