Sleeves designed for regular or standard sized 3 1/2 X 5 1/2 (9 cm X 14 cm) postcards. 3 1/2 X 5 1/2 is a common size for most older cards made in the early 20th century, and exending through late 1960s. The larger 4x6 format is generally found among postcards starting in the 1960s to current day.