THIS KIT CONTAINS 5 DIFFERENT NOZZLE SIZES 37, 40, 42, 45, and 47. For smaller sizes check part #pn21-2535. A wide selection of discharge nozzle sizes is invaluable to properly tune an accelerator pump system. The hole size determines the rate of discharge. A larger hole will shoot fuel at a faster rate with less pressure than a smaller hole. Nozzle sizes are stamped on each shooter (for example, a 25 stamp indicates a hole size of .025).