I bought the Series 2 bottle after having the Series 1 bottle since launch. The Series 2 bottle is a great design visually, but from a practical stand point, it is poor. The collar screws into the bottle, and the screw cap into the collar. The screw cap doesn't have a gradual close to it, it just stops. It is very very easy to knock the screw cap so it comes undone. The only way to keep it tight is to screw it on that much, that when undoing, the collar comes with it. So to use this bottle, you either need the screw cap slightly loose, or have to have the collar come off each time. The silicone base also arrived hanging off. I contacted chillys to return it 3 days after i received it. I explained that the screw lid wont stay in unless you tighten that much the collar comes out. They gave me a canned response for how to tighten the screw cap, and keep the collar on, it is clear that they have had to tell a lot of people about this. Ultimately it is a bottle. You shouldn't need to have to manipulate it in a certain way to open it and use it correctly. This is a design issue. A simply divot system would fix this compeltely. They have refused a refund on health and safety grounds. Unfortunately for Chillys, the bottle as is, isn't fit for purpose so I am contacting trading standards.