Since I watch these trades daily, the best I can figure is that their turning the same 2,3,4,5,6,7 thousand share lots by buying them at the bid and selling the same lot at the ask for a penny profit. If it runs on them they just square up and start the whole process over again.......I was thinking that perhaps they were there to embellish the volume for some reason. But that's just my warped conspiracy mind at work.