In 1603, James VI of Scotland inherited the English and Irish thrones creating the United Kingdom of Great Britain. In April of 1606, he introduced the King's Colours as a new flag representing the union of England and Scotland.
The flag would serve as the flag of the United Kingdom from 1606-1801. It was not adopted by Scottish military forces until 1707.
In 1801 the cross of St. Patrick was added to create the current Union flag.
The flag is 3'x5' and made from a premium 100 denier polyester. It has a white header with two grommets. There are four rows of stitches on the fly and two rows on the top, bottom, and header side. The image is screen printed and appears on both sides. Writing will be reversed on the back.
3'x5' flags are 3 feet x 5 feet, 36 inches by 60 inches, 91 cm by 152 cm, 1 yard by 1.7 yards. This is the most common size flag you see hanging on porches, small flag poles, hanging at festivals, and inside of bars and restaurants.