Fold down the jacket and put it on the pillow case. Will it be a pillow pillow?
Pillows should be used with a high degree of fit, especially if you can hold your entire shoulder or neck. Otherwise, it will affect your sleep and your body is not very good.
If it's just an emergency, just use it for a while. But if you use it for a long time, it's bad for your cervical vertebra.
