This is an adapter to fit on the Wanhao i3 plus filament holder to then be able to accept items from my dovetail mounting system https://www.youmagine.com/designs/dovetailed-mounting-system (for origional system and parts) also includes a 1kg spool holder, and a spacer to raise the spool holder to accept my large loose filament holder ( photo shows it with flexifilament loaded). https://www.youmagine.com/designs/comprehensive-filament-holder 1/5/2017 update. Correction to hole sizes on spacer block, Bottoom holes are now Diameter 5.5mm and the Top holes are Diameter 4.3mm to be tapped M5