There are many types of nozzles available with each providing different flow rates, spray angles, droplet sizes, and patterns. Some of these spray tip characteristics are indicated by the tip number.
Each type of spray tip is rated under different operating conditions. For example, TeeJet® standard flat spray tips are rated in GPM (Gallons per Minute) whereas the TX ConeJet® hollow cone tips, which have much lower capacity, are rated in GPH (Gallons per Hour).
Remember, when replacing tips, be sure to purchase the same tip number thereby insuring your sprayer remains properly calibrated.