This 550ml water bottle is designed to be lightweight and uses the thinnest possible BPA-free plastic construction, while maintaining structural integrity. It features an easily compressed design, so it can spring back readily and fit securely in your bottle cage. This is especially handy when the altitude or heat changes the pressure within your bottle. Nukeproof has also ensured that this version's wall thickness is thin to maintain its structural integrity. The two-piece cap is quick to remove and provides an opening to the bottle that can easily accept a powder scoop, making it easier to fill your bottle with your preferred mix. There is also an added lid to keep the mouthpiece clean for you to drink from.