Is Sttoke leak proof? This is a question we get a lot. The new version of the Sttoke cups (with volumes of 12oz and 16oz) with a screw-in lid and a flip-up drinking cap are leakproof. These cups were redesigned and upgraded from the older models. The 8oz models of the Sttoke cup remain non-leakproof with the older pull-out lids.
The new Sttoke screw-in lids are not backward compatible with the old version of the Sttoke cups, because the older versions will not have threads present for the screw-in lid to work. However, do be careful when storing very hot liquids in your Sttoke cup. We recommend that you flip up the lid to reduce pressure before unscrewing the cup.