diameters the use of the interchangeable pre orifice 24 24 u2032 in each purge line 22 22 u2032 allows the purge line to be calibrated in order to effectively purge the conduits 18 18 u2032 based on the type of paint or viscosity of the paint being used by the paint spray tool 10 upstream of each interchangeable pre orifice 24 24 u2032 is a main orifice 26 26 u2032 which has a valve 28 28 u2032 that functions to open and close the main orifice 26 26 u2032 in order to control the purging of paint from the conduits 18 18 u2032 through the purge lines 22 22 u2032 having an interchangeable pre orifice 24 24 u2032 allows you to control the flow of paint through the purge lines 22 22 u2032 without having to completely remove and have multiple main orifices 26 26 u2032 and valves 28 28 u2032 in order to accommodate paints having various viscosities the interchangeable pre orifice 24 24 u2032 can be interchanged with an alternate orifice 25 25 u2032 having different dimensions and orifice diameters compared to interchangeable pre orifice 24 24 u2032 the paint spray tool 10 also has a bell cup 30 connected to the body 14 and circumscribing the spray outlets 20 20 u2032 the bell cup 30 helps to prevent back spray of paint and control the spray direction of the paint leaving.