18mm Stopper for cleaning your piece
No adhesive used
Fits snug, zero leak
Can also be used as a whiskey decanter plug 
Shown in pics is an example of one on a tube I currently have for auction. This is the biggest one I have. 
Made by LilBen
A bunch of you asked me for some, so hmu! I have less than 20 left! Got some cheaper clear ones too. 
Dm if you want to see the other stoppers
This one is a bit more expensive because of its size but the others will be 20-50 shipped. 
I'll add it to whoever wins the purple rain tube 💜 for a reduced price. 

Worked glass cleaning stopper