No collection of homebrew supplies is complete without the convenient simplicity of a rubber stopper. This #10 solid rubber stopper is designed to prevent oxygen from wreaking havoc with your fermenting process. Just slide it securely into the mouth of any carboy or fermenter and the snug fit will create an airtight seal. Get your hands on this rubber stopper today and get ready to enjoy first-rate fermentation. For best results, measure the diameter of the mouth of your carboy or fermenter and compare to rubber stopper measurements to find a good fit. In stock and ready to ship. Made of rubber. Creates an airtight seal in the mouth of your carboy or fermenter. Dimensions- 1 5/8" bottom diameter, 1-15/16" top diameter.