Follicular isolation technique (FIT) was based on the idea that people were just putting the punch in and not trying to determine the depth of the follicle as well as where the dermis of the skin ended and the fat began. FIT sets a limit to the depth that a surgeon enters the skin with the punch in order to get to the beginning of the fat. The surgeon can then dissect the rest of the way or pull out the graft so there is less of a chance of transection.

The other aspect of FIT is that it is follicular isolation as opposed to follicular unit extraction which means the surgeon can take the entire unit if desired.

There are times a doctor might take only a portion of the unit and leave some hairs behind to help camouflage the donor area better. The hair left behind will continue to grow while the hair that is removed will not grow back.

FIT can also be used for eyebrow or eyelash reconstruction because it is the same approach as the scalp. The surgeon just needs fewer hairs to do it than doing a hair transplant.

Body hair can also be used but the hair is often not the same caliber nor does it grow like scalp hair or eyebrow hair. Taking scalp hair to do an eyebrow case means that hair basically retains the qualities of the scalp hair.