Note: The fermentation airlock can be matched with a silicone plug. It is suitable for most fermentation barrels. The exhaust aperture of the fermentation barrel is suitable for silicone plug. Specifications: Name: S-type One-way Fermentation Airlock Material: food grade PP Size(about): total length 17cm/6.69in, lower diameter 1cm/0.39in Plug No.3(about): Upper diameter 23mm/0.91in, lower diameter 17mm/0.67in, height 26mm/1.02in, opening diameter 8mm/0.31in, applicable exhaust hole 19-21mm/0.75-0.83in Plug No. 4: upper diameter 26mm/1.02in, lower diameter 19mm/0.75in, height 28mm/1.10in, opening diameter 8mm/0.31in, applicable exhaust hole 21-24mm/0.83-0.94in Uses: Unidirectional exhaust. During fermentation, the internal gas is discharged to prevent the external gas from entering the infection. Need to use with plug. Packing List: #productDescription h3 { margin: 0.75em 0px 0.375em -1px; }