Batman Invitations & Envelopes. Joker has taken over the Batcave and he has Alfred hostage! Send the JLA these Batman Postcard Invitations and get them to help. Each 4.25" by 6.25" card is decorated with a picture of Batman punching forward, the edge cut to match his head. Write the details of the party on the back of the card! The pack include 8 invitations and 8 envelopes. Size: 4 1/4" x 6 1/4"