The circles on the SVP are about 3.25" diameter and quite functional, looking similar in scale to the picture Ed posted above. You don't get any vernier scales though.

They aren't perfect, as the printing isn't real accurate, on mine anyway. There's about an extra degree of spacing between adjacent hash marks near one of the 0 Dec marks and also at the 12 RA mark. Not enough to make too much of a difference, practically-speaking, as long as you aren't expecting too much.

Mike