You are buying a re-manufactured Soda syphon spare part. This part is suitable for the Sparklets brand soda syphon bottles shown in the first picture and many of their close variants.
This listing is for a rubber neck seal and borosilicate glass dip-tube which is suitable for use with the Sparklets Types C and D syphons and also Aerators "Prana" type C, Double B and similar soda syphons from about 1920 and onwards to about 1955. Like some of the original Sparklets glass dip tubes, this re-manufactured design has a lip on top of the tube which prevents the tube being blown down into the soda syphon body when the rubber washer stretches with age.
The dip-tube is made from a temperature and shock resistant grade of glass similar in properties to "Pyrex" and so is resistant to the rapid changes in temperature created when charging these types of soda syphon. However, it is still glass and should be treated carefully when being used as may not survive being dropped onto hard surfaces or floors.
The kit comes as a new glass dip-tube (26cm long) which will fit nearly all syphons of the types mentioned above (please be aware that it may not actually touch the bottom of your glass syphon as there were some variations in the depth of the bottles during original manufacture). If the glass tube is found to be a few mm too long it can be raised slightly above the surface of the seal without reducing its effectiveness during use.
Diameter at the top of the washer is 32mm and thickness is 4mm. Central hole diameter is 7.7mm. The tube is of 8mm diameter, except at the top where it is flared to 10-13mm in diameter.
Due to the fragility of these items they are dispatched within a rigid plastic tube to prevent breakage. Packaging should be opened carefully in case the tube drops out as it may be loose within the tube.
See my other listings for sparklets period accessories.
P. S. If you happen to have a Sparklets soda syphon that you would like reconditioning, please see my other listings.