a follicular units grow in groupings of 1,2,3 and occasionally 4hairs. There are always going to be more 1 hair grafts, then the next most will be 2 hairs, followed by less 3 hair groupings, with the least amount be 4 hair follicular units. It is all best to use the single hair grafts in the hairline and then follow up with 2 hair units right behind the single hairs. 3 and 4 hair follicular units should be used behind the 1 and 2 hair groupings and used more for density.