pearl size comparison
Some quick guidance:
Having said that... if you're like us, it can be hard to 'visualize' what a 4mm or 8mm or any "mm" pearl size really looks like. And posting an image online isn't so good since they vary in size based on your monitor/resolution.
So here we're going to list some common pearl sizes compared to 'real world' objects that may be easier for you to picture: