The Manfrotto 188 adapter features a 3/8 inch threaded hole at one end and a 5/6 inch (16mm) hole on the other.
Silverline 6 Core 12 Piece diametermond Core Drill Kit 38 to 127mm
Dellorto DHLA Main Jet - 188 (227484-188)
Manfrotto MOVE Adapter 75mm To 60mm SNG Fast/535
Manfrotto 120 3/8 to 1/4 inch Adaptor
Manfrotto 125 3/8 to 3/8 Short Adapter Spigot
Manfrotto 170 Mini Floor to Ceiling Pole
