Hexagon bar is a hexagonal (six-sided) cross section, size (Diameter) is specified by the distance across the flats.
304 stainless steel is an austenitic steel and is one of the most widely used stainless steel alloys due to its excellent corrosion resistance, good strength, and ease of fabrication.

Material: Stainless Steel
Shape: Hexagon Bar
Alloy: 304
Temper: Annealed
Diameter: 0.375 (3/8 inch)
Finish: Cold Finished
Specifications: AMS 5639, ASTM A276
Tolerances: Diameter: (+0/-0.003) | Length: -0/+0.999)