The Eastman Kodak Company
In 1963 the Kodak Instamatic cameras were introduced. These used roll film in cartridges from drop-in film loading. The image size is 28 x 28 mm, but slight masking is required in printing and slide mounting so the useable image is 26.5 x 26.5 mm. The number 126 was used, as the original roll film for this size had been discontinued in 1949.
For the Kodak Pocket Instamatic cameras introduced in 1972, a number lower than 126 was preferred, partly to indicate a smaller image than the 126 film. The number 110 was chosen because it could be said as "one ten" and was easy to remember.