Dispensing assembly including an additive mixing device

A dispensing system comprising:

• a container containing a flowable base formulation to be dispensed;
• a plurality of additive mixing devices, each device comprising,
• a body having an internal cavity for receiving at least a Portion of said flowable base formulation,
• an input into the cavity,
• a dispensing output from the cavity,
• a respective additive ingredient impregnated within a carrier material and disposed within the cavity, and
• a mixing structure within said cavity between the input and the output;
• and
• an actuable pump engine between the container and the mixing device,
• said input of each of said plurality of additive mixing devices and an output of said pump engine including mating formations whereby each of said plurality of additive mixing devices is removably mated with an output of said pump engine and selectively interchangeable,
• said pump engine drawing said flowable base formulation from the container and pumping it through the respectively installed one of the plurality of mixing devices, wherein said respective additive ingredient is introduced into, and mixed with, a flow of said base formulation traveling through said mixing device with each actuation.