These are acupressure pads which can be used to build a acupressure mat or work a replacement parts for missing pads.

What ist an Acupressure mat?

Acupressure mats kind of look like short yoga mats that have plastic spikes covering the surface that are designed to apply pressure at points throughout your body. Some of them also include a pillow that allows you to apply the pressure to your neck as you lie on the mat