This is Dremel's 3/8" Flapwheel (120 grit) Accessory Bit.

FEATURES: A wheel of 120 grit abrasive strips.
          Flapwheels grind and polish flat or contoured surfaces.
          Used most effectively as a finishing sander after heavier surface
            sanding and material removal is complete.
          Use on surfaces such as metal, wood, rubber and plastic.
          As the flapwheel wears down, new abrasive is continuously exposed,
            preventing clogging and providing uniform finishing throughout the
            life of the flapwheel.

INCLUDES: One Flapwheel Bit

REQUIRES: Rotary Tool

SPECS:    Flapwheel Diameter:  3/8"  (9,5mm)
          Shank Diameter:      1/8"  (3,2mm)
                                                                      kr9/26/01
                                                                          ir/kh