These unique colour-changing cups are fun and safe to use again and again. Made from BPA-and lead-free materials, they fit most cup holders. This six-pack set comes with six mix-and-match colourful and stackable cups with splash-resistant lids and straws. Add any iced beverage to activate the colour change and start the party!This water bottle is practical in design while also being fashion-forward. The colour change effect is dependent on ambient temperature. For greatest impact rinse cold cups in warm water before use. Wash before first use. No abrasive cleaners.