The DPK dosing unit is a compact, loss-in-weight, precision feeder, suitable dosing small quantities of colour or additives into a flow of base resin. The masterbatch or additive to be dosed is contained in a hopper made of a specific transparent shock-resistant acrylic material, free from electrostatic charges, which makes immediately visible the material contained and the load level. The additive hopper is easily removed with no tools for the quick change of the recipe.