This is a /Manfrotto 241FB Pump Cup for lightweight photo/video equipment. The disc's diameter is 5.8" (14.7 cm). It weighs 1.36 lbs (618 g) and has a 3/8" thread to accomodate most any Bogen/Manfrotto head. The pump adheres the base to flat, non-porous surfaces.
Replaces part number 3500.
Stellar Lighting Systems