i go with these....real simple....i send out the pics to debbie at splitendshairreplacement and all i have to do is do a slight blend around the edges with a razor comb.....the black and white pic shows hair i cut my bio hair the color pic is how she cuts piece.
i do my bio hair myself....i use a #3 guard for the bottom most portion....followed by a #5 from the bottom to the top and then a #4 from the bottom to center...then go over the whole thing with the #5 again to make sure there arent any lines

this is the razor comb

https://www.amazon.com/Diamond-Edge-Plat...razor+comb