We usually see 4 digits before the propeller. The first two digits refers to the diameter of the blade, which is the length from one end to the other paddle head. Units is Inches. It should be noted that 10 or more refers to 10 inches!
8040 propeller refers to 8 inches diameter, screw pitch 4 inches
9050 propeller refers to 9 diameter, screw pitch 5 inches
9047 (also known as 0947) 9 inches diameter, screw pitch 4.7 inches
1047 propeller refers to 10 inches diameter, screw pitch 4.7 inches
1260 propeller refers to 12 inches diameter, screw pitch 6 inches
The length and the screw Pitch of the propeller indicates the Blade specifications, the longer the length and pitch, the greater the required level of the motor or engine.