23 of 24 each is 2.75x4.5" on stiff paper. 1950s issued one per box of Rice Chex and Wheat Chex. Each front has bw image and point of cards were to stare at center dot for 30 seconds, then at a wall or the in the sky to see "Huge Magic Space Picture" optical illusion. Images include cast members, space craft, insignia, cosmic ray gun, etc. Back include info on that image along w/cereal ad. Missing only card #16. All have some degree of age toning. Otherwise just lt. handling wear. Overall EX. Scarce series.