What does the designation MS20426AD-6-5 indicate about the countersunk rivet?

The designation MS20426AD-6-5 provides specific information about the countersunk rivet, particularly regarding its length. In this system of designation, the last number, which is "5" in this case, indicates the length of the rivet in 1/16-inch increments. Therefore, to determine the length, you take the value "5" and multiply it by 1/16 inch.

When you calculate this, 5 multiplied by 1/16 inch equals 5/16 inch. This is why the correct interpretation of the designation points to a length of 5/16 inch for this specific rivet type.