Metal tubing size is determined by the ________ and is measured fractionally in ________ of an inch.

The correct answer highlights that metal tubing size is determined by the outer diameter, which is essential for ensuring compatibility with fittings and connections in fluid systems. The measurement of the outer diameter in sixteenths of an inch is a standard practice in many industries, particularly in applications where precise fit and function are necessary.

Using sixteenths is advantageous because it provides a finer granularity than other fractional measurements, allowing for more precise sizing. This precision is critical in ensuring that the tubing fits correctly with other components, maintaining the integrity and performance of the fluid system. The significance of outer diameter lies in its role in fitting compatibility, affecting how well various components connect without leakage or pressure loss.

This method of sizing is prevalent in engineering and mechanical applications, reinforcing the importance of accuracy in design and assembly of fluid lines and fittings. Thus, understanding that outer diameter is the defining measure for metal tubing size, and knowing that it is measured in sixteenths, is crucial for anyone working in this field.