Tritan is the new, yet unproven substitute for BPA containing polycarbonate (Lexan). Tritan is definitely softer than polycarbonate, and in my experience, the lids don't screw on as easily as the old polycabonate bottles. I'm going back to the HDPE bottles, which I have always used for backpacking because they are lighter and you can see the buggies when you collect stream or spring water. HDPE does stain more easily and sometimes give off a plasticky taste, though.Nalgene only introduced the Tritan product to replace Lexan bottles.