This smaller Hokkaido roller has a very unique feature; it's internally frosted.

Internal frosting happens when there is sand, shards of glass, or other debris trapped inside the float that's tossed around enough to where the inside surface of the glass becomes frosted.

This is one of a handful of interally frosted rollers that I've seen or even heard of. From my experience, it's much more common to see glass balls with internal frosting than rollers.