Final answer:
The max length of a beard authorized for medical treatment (shaving profile) is typically a quarter inch, but this can vary depending on military branch regulations and country.
Step-by-step explanation:
The maximum length of a beard authorized for medical treatment, also known as a shaving profile, can vary depending on the specific regulations of the military branch or organization. Generally, a shaving profile allows service members to keep beards of certain lengths due to medical conditions such as pseudofolliculitis barbae (PFB), which is an irritation caused by shaving. For the United States Army, for example, the maximum length allowed under a shaving profile is usually a quarter inch (1/4 inch). However, specific requirements and maximum lengths can differ by branch and country, and individuals are expected to follow the instructions of their commanding officers and medical professionals.