They look a bit like some of the suckers you can get for the hoppers, specifically the arm that opens the folded section. I think maybe they are used where a traditional sucker marks the job or to blank the ones that fall outside the job.
Very useful sucker. Essentially they are used in conjunction with a formed cap (Black) that goes on the opposite drum (Gearside) in the pockets for opening sigs on Vacuum. Typically they can get you over the hump on exrtremely heavy stocks. Leave no doubt that they are a good item to have in the arsenal but you really need the cap that mates to it for the effectiveness....