It's the inside of edible crab. It's hard to keep on your hook from what I gather. Some people use finger gauze, others wrap it in cling film nd pierce the film as it goes on the hook. Good cod bait. Illegal to use north of the Tyne I think (never seen the cart cops though). Haven't seen it in many shops but av never really looked. As for the quality I think people tht use it tend to make it them selves. This might be wrong but it's what I've picked up from other threads, never used it or seen people use it yet. If anyone knows a shop with decent cart that they've used please shout up.