Try it on for size!
For use with regular or wide-mouth Mason jars that you may already own, these inexpensive valve-and-weight sets simplify the process of fermenting small batches. The glass weight helps keep ingredients submerged, while the jar's threaded collar holds the silicone airlock in place, acting as a one-way valve to keep air out but releasing built-up pressure so you don't have to monitor it constantly.
Simple and effective.