Avery Ink Jet Postcards/Index Cards 400 Cards

Avery #8577 Ink Jet Postcards/Index Cards 400 Cards - 4 cards per sheet 5 1/2" x 4 1/4" I've had this package for a few years and it's never been opened. I planned on using them for handouts but never got around to printing the cards. I'm not sure what the cards look like or how thick the card paper is.