Split-Tpye Fermentation Kit: The fermentation lids is highest quality, food grade material, BPA free. Easy to put on and take off and clean, you can easily separate every part of the jar for cleaning Mason Jar Fermentation Kit: The gas escapes without allowing air in. It can easy release airlock to automatically let carbon dioxide out all while blocking oxygen, and any nasty airborne agents from entering your jars. included a extractor pump to suck out the oxygen during the later stages of your ferments Date Tracker: The built in date dial means you’ll always get the timing right. You can track both month and day when your ferment started, so you always know when it's almost complete and get delicious fermenting foods on time Fermentation Weights: Great tool for fermenting & pickling, and a great addition to your fermenting hobby. Effectively keep ferments submerged below brine for best results with a fermentation weight. You will also receive a detailed user guide to learn how to ferment any of your favorite delicacies 100% Satisfaction Guarantee: Each set has four lids, which are compatible with the wide mouth bottle you already have, four gravity rocks, a vacuum pump and a detailed instruction manual.Our fermenting lids for wide mouth mason jars supports our manufacturer's 30 day money back guarantee and 1 year free replacement guarantee