It's secure, carto tanks use the same method and they are flawless in that department. Cap threads onto the top ring in kit, then Orings n glass then the bottom threads on to the kf base, it's a good setup, you'll like it, those juices prolly will be fine with the stock window but I'd get the kit neways, it's nice n good looking, and you won't ever have to worry about other juices.