A aluminum sheet 16 gauge refers to an aluminum sheet that has a thickness of 0.0508 inches or 1.29 millimeters. The gauge measurement system is commonly used for sheet metals, where a higher gauge number indicates a thinner sheet. In the case of aluminum, the gauge measurement is based on the weight per square foot of the sheet.
It's important to note that the gauge measurement system can vary slightly depending on the country or industry. The information I provided is based on the standard gauge measurement used in the United States. If you are in a different region, there might be variations in the gauge-to-thickness conversion.