Straw - made of borosilicate glass by the Czech company Technosklo Držkov; on the Mohs scale of hardness, where a diamond has a hardness value of 10 and chalk a hardness of 1, borosilicate glass is rated 7.5, whereas regular glass is 5.5-6; borosilicate glass does not absorb odours and can be reused without releasing unwanted chemicals, dishwasher safe, cleaning brush included, it is not advisable to bite these straws and so children under 12 years of age should only use them under adult supervision; eco-friendly replacement for plastic straws