Hejnar Photo 8.3cm conversion Clamp for Manfrotto 054, Manfrotto 055 Manfrotto 057 Magnesium Ball Heads and Manfrotto 494, Manfrotto 496, Manfrotto 498 Ball Hads. Conversion clamp is attached to Manfrotto head after removing original Manfrotto Platform in just a few simple steps: 1) Remove original Manfrotto platfom 2) Align slots on clamp back with island on Manfrotto post. 3) Attach clamp in place of original Manfrotto platform using original centre screw. Compatible with Kirk, R.R.S., Arca-Swiss, and many other Arca-Swiss style Quick release plates. Made in USA.