You are buying a re-manufactured Soda syphon spare part. This part is only suitable for the original Sparklets brand soda syphon glass straws shown in the pictures.
This listing is for a rubber neck seal which is suitable for use with the plain (straight sided/topped) or flared ended glass straws often found in 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.
The dip-tube seal is made from a food-use approved synthetic rubber (hence the blue colour) and its composition has been certified by one, or more, of the FDA, UK Water Research Association or an EU approvals body.
The kit consists of just the blue rubber ring/washer shown in the pictures and does not include the glass straws also shown in the pictures, which are present for illustration purposes only. The soda syphons shown in the pictures are only present for illustration purposes - to show the syphons which this type of straw was originally fitted to - and are not included in the item sale which is just the blue rubber seal.
Diameter at the top of the washer is 30mm and thickness is 6mm. Central hole diameter is approximately 8mm.
It is strongly recommended that this seal should be softened in hot water prior to fitting it to the glass tube as this softens the rubber. Tubes of over 9mm in diameter may require the hole to be enlarged slightly before fitting. Fit the seal onto the glass tube whilst still warm and allow to cool in place. The seal can be lubricated (if required) by use of either culinary grade glycerine or just water. As the original glass straws are prone to breakage care should be taken when fitting and using them. When fitting seals to glass straws use protective gloves or hold in a cloth. Do not use excessive force or breakage of the straw may occur!
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.