I am a surgeon, and I will answer this question for you, because in the medical industry, the black line means it is non-absorbable, which is what everyone knows by default and does not need to be marked. There are also non-absorbable ones such as dark blue ones, but there will be a logo on the outer packaging, which will say "non-absorbable thread". Most of the absorbable threads are milky white, transparent and purple. The appearance of these The packaging will be marked with the words "absorbable". The absorbable thread will generally be converted into water and carbon dioxide after 50 days, while the non-absorbable black thread will not change. The absorbable thread is much more expensive than the black thread and is generally used for internal sutures. That is, it cannot be seen from the outside, and the black wire seal on the outside needs to be removed. Hope this helps.