Yes the 74-580 sandpaper is compatible with the mouse and mega mouse sander
This model of the polishing/sanding kit 74-580 does not have holes.
This kit includes two no. 0 polishing wool pads, two 180-grit sandpapers, two 220-grit sandpapers, five finger tips, and two foam pads.
Yes, the 74-580 will work with your MS800 sander.
The sander it's self has a rough velcro like surface of a knobby plastic like material. The Sandpaper sheets come with a fluffy side almost like a little flannel on the back. They stick right together!!! Very snuggly. The tip out in fron wears out quicker when you are doing pointed sanding, so the two ears of diamond shapes out there are actually "refills" so when you wear off the tip, you pop on a new little tip. Those are still attached to the sheet as a manufacturing process. You do not use the sheet with the two side pieces attached. They rip right off....
This is for a Black + Decker model.