According to the U.S. Patent & Trademark Office, electric heating pouches are medical apparatus, namely, electric heating devices for curative treatment.

The U.S. Food and Drug Administration

Food and Drug Administration

The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 (FDA) classifies the heating pouch as a class II medical device.

Heating pouches are sometimes mislabeled as "heating pad

Heating pad

A heating pad is a pad used for warming of parts of the body in order to manage pain. Localized application of heat causes the blood vessels in that area to dilate, enhancing perfusion to the targeted tissue...

s". Heating pads are, by definition, flat, whereas heating pouches are contoured or curved.

In order to achieve the geometric design, three uniquely-made heating pads are placed within a PVC

Polyvinyl chloride

Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...

 pouch to form a scoop-like shape.

Heating pouches are made specially for human body joint

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

s; specifically the shoulder, elbow, hip, knee, ankle, and wrist or hand. The curvature of the pouch enables the user to completely cover these joints, whereas flat heating pads cannot conform to the curved joints.