The Topaz Rainbow Beaker Glass Bong is 200mm of strong Pyrex glass that is coloured like a rainbow. Although more expensive glass is the best material to choose for a bong, it's a lower maintenance option. The traditional beaker style of the Topaz glass bong is one of the reasons it is popular as it looks like it should be in a lab. The beaker is flared at the base which makes it much sturdier than other bongs of this size.