Manfrotto Fluid Base with Retractable Reet for Monopods (ø20mm tube) Fluid base that quickly transforms a photo monopod into a video monopod adding the fluidity feature onto the PAN movement. MVA50A can be easily attached on the last section of a photo monopod & is suitable for: Manfrotto 679B, 680B & 558B, all monopods featuring a ø20mm tube in the last section.