1" to 1.25". Issued in the 1930s, there are two distinct six button sets. The first set has back papers w/text reading  “World’s Most Famous Planes” as well as naming “the two greatest scientific strides” as “1 Aviation/ 2 Vitamin D Bond Bread.” The second set of six was issued without back papers but whereas the first six have a blank top margin the second six have Bond bread promotional text. In each set, five buttons have identical planes pictured with identical text. These five planes were piloted by #1 Lindbergh, #2 Post and Gatty, #3 Byrd, #5 Amelia Earhart, #6 Floyd Bennet. On button #4, blank top rim set shows plane of Coste and Bellonte while set with top rim slogan #4 shows “Autogiro”.  These 12 are totally clean and Exc, although #5 with top slogan has edge bump from imperfect crimping at 3-4 o’clock. With these 12, are three added Bond Bread buttons. The 1” is clean but has some scratches while the 1.25” pair are Exc.