Kids get an up-close look at the solar system, our changing Earth and the four seasons! Each plastic viewer comes with disks featuring images that bring science to life. Children slide a disk into the viewer and pull the lever to look at one photo after the next! Each viewer comes with 4 disks, 28 total photos and a full-color booklet packed with interesting facts. Complete set includes all 3 viewers shown, for a total of 84 photos. Viewers measure 4 1/2". Each viewer also available separately.