The attachment for fruit, Soft Fruit Knob, has a softer spring tension to allow soft fruit pulp to come out of the machine. If the knob is not installed, the pulp may come out before time–you will have wetter pulp and less yield of juice.The normal Outlet Adjusting Knob has a hard spring tension to allow hard vegetable fiber like carrots and greens to remain in the machine so it is still juiced, and will come out dryer. If juicing apples and carrots, use the regular knob. Put in the apples first and then the carrots (the fiber in the carrots help push the soft fiber of the apple through the machine).Refer to the Greenstar GS-P501 / GS-P502 / GSE-5000 / GSE-5010 / GSE-5050 / GP-E1503 / GS-1000 user manual for more information.