> The dimensions of DL [size] are 110 x 220 mm (4⅓" x 8⅔") and as such the DL envelope will hold an A4 sheet of paper folded into 3 equal sections parallel to its shortest sides.

* https://www.papersizes.org/c-envelope-sizes.htm

* https://www.youtube.com/watch?v=DmBvP0KOZP0