There is two variants of this. One is for PET bottles, where the bottle cap is a press fit in the "feeder" part. Not all bottle caps are the same, so find one that fits. Drill a big hole (12mm or upwards) in the cap, screw it onto the bottle, and press it in. Make sure to use a sturdy, thick-walled bottle or the vacuum will crumple it and it will not work well. The other version is for 2l glass bottles (known as "Doppler" in Austria). There are rubber caps avialable for those bottles (e.g. https://www.kochen-essen-wohnen.de/suessmostkappen-groesse-2.html) that provide the seal between the "feeder" part and the bottle. Cut a hole into that rubber cap, again as big as you can, slide it over the bottle neck, and press it into the feeder. I provide two ring sizes, you may want to scale them up or down depending on your bottle diameter. The "holder" part is to be screwed down to a base plate and keeps the feeder in place. To mount the bottle, turn it upside down, hook it into the ring and drop the "feeder" into the "holder".