Give some stream of consciousness and then the answer. If donor hair numbers from the back of the head are insufficient, it is possible to perform body hair transplantation (BHT) on appropriate candidates who have available donor hair on the chest, back, shoulders, torso and / or legs. Body hair transplant surgery can only be performed by the FUE harvesting method and, so, requires the skills of an experienced FUE surgeon. However, there are several factors for a potential BHT candidate to consider prior to surgery. These include understanding the natural difference in textural characteristics between body hair and scalp hair, growth rates, and having realistic expectations about the results of BHT surgery.

Based on this passage, where does the hair from a hair transplant come from?
To answer this question, we should know that: If donor hair numbers from the back of the head are insufficient, it is possible to perform body hair transplantation (BHT) on appropriate candidates who have available donor hair on the chest, back, shoulders, torso and / or legs.
Therefore, the answer is If donor hair numbers from the back of the head are insufficient , it is possible to perform body hair transplantation ( BHT ) on appropriate candidates who have available donor hair on the chest , back , shoulders , torso and / or legs.