Astrophysicists are leaving no stone unturned in their search for what dark matter is. Different particles have been proposed, like WIMPs and axions. Hypothetical rimordial black holes have also been proposed. But there's another less well-known candidate, SLABs or Stupendously Large Black holes, a sub-type of primordial black holes. Alas, SLABs can't account for dark matter either, according to new research.