Beakers, flasks & graduated cylinders have graduation markings while all test tubes are unprinted. Test tubes & flasks have thick tooled rims for safe stoppering. Dimensions listed under item Specifications are external dimensions e.g. an 18mm test tube is 18mm (+/-) OD.
Borosilicate glass, commonly referred to as "pyrex" is used in all quality lab glassware. It's resistant to thermal shock and food safe because it is completely LEAD FREE! See the tables below for physical & chemical characteristics.
Glassware cannot be returned for any reason; this is for your safety and ours. It would be prohibitively expensive to test for bacteriological, chemical or radiological agents since there is no way to tell if glass has been contaminated just by looking at it. We would have to throw it away even if you claim to never have opened the package.
However, if the item is broken, clearly defective in some way such as severely bubbled or chipped, send us an image & we will refund you.