The four-digit number refers to the outside diameter and wall thickness of the shaft. The first two NUMBERS are the APPROXIMATE outside diameter to the nearest 64ths of an inch. The second two numbers are the wall thickness in thousands of an inch. For example, a 2514 shaft would be APPROXIMATELY 25/64th of an inch in diameter and .014 of an inch wall thickness (EASTON controls ACTUAL dimensions to 5 decimal places). OD and wall thickness are the two variables in controlling spine for ALUMINUM arrows.

The four-digit number refers to the outside diameter and wall thickness of the shaft. The first two numbers are the APPROXIMATE outside diameter to the nearest 64ths of an inch. The second two numbers are the wall thickness in thousands of an inch. For example, a 2514 shaft would be APPROXIMATELY 25/64th of an inch in diameter and .014 of an inch wall thickness (Easton controls actual dimensions to 5 decimal places). OD and wall thickness are the two variables in controlling spine for aluminum arrows.