All Bomma products are hand-made from mouth-blown lead-free crystal. Therefore any small bubbles, non-melts and irregularities in the glass are both proof and a characteristic feature of this traditional craft. The Pebbles Collection is made by underlying colored glass technology. Thanks to the manual process of blowing underlay glass, each piece is an original. Individual products may vary slightly in intensity, hue or even color. This is an accompanying characteristic of the traditional underlay glass technology