Practical and very clever! This double walled tea maker is perfectly suited for on the road. Just add your favourite tea to the tea leave compartment and pour hot water into the double walled glass mug. Then screw the glass and tea leave compartment together and turn the tea maker upside down to start the brewing process. After the desired brewing time just turn the tea maker back around, take off the tea compartment and enjoy your tea. The glass mug can always be locked by the integrated clip lock button, so no fluids can enter the tea compartment. This is very practical while on the road. The borosilicate glass tea maker, with polypropylene lid and sleeve includes a fine tritan filter.