Rocailles Preciosa are the most used type of glass seed beads. They were created in Venice, Italy in the 15th century. These beads have been produced industrially in Bohemia since the 18th century. These round seed beads are manufactured using unique technology for cutting glass tubes with round or square holes into various sized pieces which are then rounded and polished when hot and subsequently classed by size and shape.
The PRECIOSA Rocailles are produced in sizes from 1.5 mm to 8 mm and the sizes of the Czech seed beads are stated using the traditional so-called zero series. The regular sizes range from the smallest 16/0 through to the largest 1/0, while rarities also include the four large sizes of 31, 32, 33 and 34, known colloquially as potatoes.