Small A1 invitation envelopes size 3 5/8 x 5 1/8 in our contemporary Euro-Flap (deep neck) style are made from Gmund Color System (28) Chartreuse 68lb text weight paper. A1 envelopes are primarily used for RSVP cards and note cards and correspond to our A1 cards measuring 3 1/2 x 4 7/8. Chartreuse A1 euroflap envelopes can be ordered blank or custom printed by the professionals at LCI Paper.