These are flake skin (shark) which has been sustainably sourced and wild caught in Australia. By utilising the skin, together with cartilage, very little of the catch is wasted - this is just like nose to tail eating for humans, where the entire beast is used. The fishing industry supplies flake for human consumption, but the skin and cartilage are surplus to their requirements - your dog would tell you that they are missing out!!
As your dog starts to chew on the rolls, they will gradually start to unravel, which will keep him entertained.
These are a really good chew for dental health as they take some work to get through.