In our economy models, only the bottom of the jaw is ground. Our smallest series the"micro" clamp is only available as the economy model (AK2-VT-SO).
The fixture's accuracy normally is assured by the precision of the positioning elements, not by the clamp itself. The clamp's job is to generate the force to hold the workpiece against the positioning elements.
OK-VISE economy models are used in regular workholding when ultraprecision is not required. They are made of the same raw materials as other models, and the bottom of the jaws is ground for precise positioning on the fixture base.
AK2-VT-SO always comes with Viton O-rings.