2. Length: The pillow should not be too long or too short when sleeping, and the width of three or four heads is better to ensure that the neck will not fall off the pillow when sleeping, which will affect the quality of sleep.
In addition, the hardness of the pillow also has certain requirements. It is best not to choose a pillow that is too soft or too hard. Too soft pillows can't provide enough support, and too hard pillows will affect comfort. It is recommended to choose a pillow with moderate height, length and hardness.