It's a specialty BMW tool (Pelican Parts #PEL-TOL-3008), and actually, it holds the little bolts so you can remove the big reverse thread fan clutch nut. But really, it's not worth buying. You can use a large allen key or screwdriver to jam between the bolts, or even make your own tool easily. I used the large screwdriver method myself.
TIS= BMW Technical Information System software. It's kinda like realoem.com and the Bentley manual combined together.