I would say the minimum is one inch..one cm is very short and the poly rim (if poly) could show. Also, blending with bio at 1 cm is much harder than 1 inch. I had a short haircut once, (with piece sides being about 1cm) and after 5 or 7 days, given my bio hair had grown, the demarcation between piece and hair was obvious, so longer you have, less maintenance cuts of your own bio hair is needed.You choose the length according to your hairstyle not the coverage of something, but I think 1 cm is minimum.
I would say the minimum is one inch..
blending with bio at 1 cm is much harder than 1 inch. I had a short haircut once, (with piece sides being about 1cm) and after 5 or 7 days, given my bio hair had grown, the demarcation between piece and hair was obvious, so longer you have, less maintenance cuts of your own bio hair is needed.