the sssnake Cable Label Holder Set Large

Great holders and price is good too. You can get the same from Ali for the similar price, but Thomann adds good paper labels. Bought several of these small and big ones - small is fine to mark only one cable, big is fine to tie both cables and mark them together. Instead of white paper I just used cheep colored paper from euroshop to mark cables (with some bright colors), so they are better visible during the day and evening.