6" diameter double stitched sisal mop designed for use with the tapered spindle adapter on either a bench grinder, lathe or bench mounted drill.
The sisal mop is more aggressive than the calico one and intended for use with black compound for first stage surface preparation prior to polishing.
There are cheaper mops on the market but quite frankly you get what you pay for, these are proper tools, robustly made from good quality materials and will last for ages. Better to bite your lip and spend the money on a decent one.
Safety note: To prevent the tool from digging in dangerously, only use in machines where the top of the wheel is moving away from the user.