This set of Artist Cards from Moab includes 1000 cards in the 4.5 x 5.8" size for printing greeting cards, invitations, promotional cards, and the like. The cards are actually about twice as large. They come as 200 gsm sheets printable on both sides, and they're inkjet-coated to support high-quality, high resolution printing of photographic and fine art images. They're made of 100% cotton and are pre-scored at around the middle so that you can fold them into 4.5 x 5.8" cards.
The cards are compatible with most photorealistic inkjet printers. Moab offers templates for Photoshop and Lightroom on Mac and Windows to help lay out your cards.