These measurements are based on the inside diameter of the hose, not the outside. The bigger the diameter, the more water the hose will carry. A hose width of five-eighths inch is generally most useful. California Prop 65: This product can expose you to chemicals including DEHP, which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.