Extra Large (18mm+)

How large a bead seems depends not just on its length but on other dimensions as well.  Thus, an 18mm bead that is 16mm wide may seem very large, whereas an 18mm bead that is 8mm wide may not seem large at all.

I carry very few really large beads.  They are expensive, hard to find, and defects on very large beads can be more apparent than on smaller beads.  Also, very large glass beads can be very heavy, which makes them impractical.