Used to provide a positive seal on your brewing vessel. Drilled hole is compatible with standard Fermentation Airlocks. BPA-free and food grade. 

• #5 pairs with our wide mouth glass carboys.
• #6 size pairs with most 1-gallon growlers (top diameter 1.25", bottom diameter 1.03", length 1").=
• #7 size pairs with most narrow neck 3 & 5 gallon glass carboys (top diameter 1.43", bottom diameter 1.19", length 1").