Small beads — small like seeds and as numerous as grains of sand! We have Czech Seedbeads and Japanese seedbeads, and a wide variety of shapes and sizes.
Smaller 11/0 -> 10/0 -> 8/0 -> 6/0 Larger
Seedbeads sizes are indicated by a numbering system. The larger the number, the smaller the bead. Size 6/0 are about 2.5 mm by 4 mm. Size 8/0s are a little smaller than 6/0s. Size 11/0s are small - size 10/0s are a little larger. To the novice beader - they will seem very similar - but with experience you can tell them apart.
Sizes 12/0 and 13/0 are smaller still, although the hole is still about the same size at the 11/0s. Size 22/0s - well - they are just mind-bogglingly small!
Size 33/0 is the exception - those are big!
The shapes other than the classic "donut" shape and small tubes are referred to in millimeters.