I bought the 500ml black chilly bottle because I drink lots of iced water as I own a ice making machine and spotted these chilly bottles on Face book and when it claimed to keep your drinks cold for 24 hrs I thought I got to give this a go so ordered one ,it was delivered within 3 days after just having just plain tap or filtered water in the bottle for the first few days I started adding ice to the bottle and found that 24hrs later there was solid ice still in the bottle and all I did was to just top up with water to the ice left in the CHILLY bottle so my verdic is I highly recommend these chilly bottles . I have even got myself a second one the smaller 260ml size for my handbag .