The 21 on Barbs CV-23 is a 14 1/2 diameter, the 23 was the OFX and it's 15 1/8 diameter, diameter is an importand concideration for chosing a prop
the one on Burning Daylight is a 14 1/4 X 23 powertech, but it has been hammered, ground on, ground off, blades thinned and sharpened, it has the performance of a 24 on the prop calculator @10% slipage, 5000 rpm - 68 mph