Hi Leongfm,
if you are intent on buying Sigg water bottles, you might want to check the insides of the bottle after using it for some time.You need to shine a light in to check.
I threw away mine after detecting rust inside, and I have no idea I drank "rusty water" for how long before that.
I have nothing against Sigg bottles, but thought Nalgene would be a better buy.
Just my personal opinion and experience.