What is the radios of .28mm?

The term "radiOS" seems to be a typographical error or misinterpretation. If you meant "radius," then a radius of 0.28 mm refers to the distance from the center of a circle or sphere to its edge, measuring 0.28 millimeters. This is a small measurement often used in contexts like micromachining, medical devices, or precision engineering. If you meant something else by "radiOS," please clarify for a more accurate response.