What is the standard size of the pillowcase?
And double pillow case, then need to be used in 5 feet bed or 6 feet bed. The 5 foot bed usually has a pillowcase of 48 * 115cm in diameter. The 6 foot bed usually uses a pillowcase with an inner diameter of 48 * 145cm.
The national standard for single pillowcases is the inner diameter of 48 * 74cm, with 2 on each bed.