When it comes to fermentation, the key is to keep the oxygen away. This rubber stopper may look pretty simple, but it plays a very big role within the process. Constructed from a solid rubber material, simply insert this stopper into the mouth of your carboy or fermenter and you have an oxygen free zone.

#6.5 Solid Dimensions: 1 1/16” Bottom Diameter; 1 1/8” Top Diameter