QUALITY RELIABLE PRODUCTS REUSABLE SILICONE SEALS STAY PUT. They are designed wide enough that they seat firmly against the roof of any brand Mason jar plastic cap completely underneath the threads and cannot fall out while screwing the lid onto or off the jar. They are GUARANTEED to provide an airtight and leak-proof seal. We tried the narrower red rubber seals with the smaller outer diameter. They tend to become displaced while tightening the lid, and unfortunately, they did not keep our fermentation jars airtight (see photo). QRP SEALS provide a perfect airtight, anaerobic enclosure while fermenting Kimchi (vegetables) or Kombucha (tea). We ferment on a very large scale, and QRP SEALS do resolve the airtight issue. When testing QRP SEALS by placing water in a jar and shaking the jar, we experience no leaks. We understand your health concerns. QRP products were developed to help our director overcome prostate cancer. ALL QRP products are made from USDA Food Grade BPA-free Compliant Silicone and are produced by a reputable food container manufacturer for food products only. CAUTION: OVERTIGHTENING COULD DAMAGE THE SEAL AND MAKE IT DIFFICULT TO REMOVE THE CAP! QRP SEALS HAVE NO TAB AND ARE NOT A GOOD FIT FOR GLASS STORAGE CONTAINER LIDS. 2016 Quality Reliable Products, All Rights Reserved. Includes 500 WIDE MOUTH SEALS for pint, quart, or half gallon STANDARD 3″ WIDE MOUTH Mason jars. QRP Wide Mouth Seals are 2mm thick with a 3.375″ (86mm) outer diameter and 3″ (76mm) inner diameter openings; lids not included. Not for so-called WIDE MOUTH GALLON jars. ALL QRP products are made from USDA Food Grade BPA-free Compliant Silicone and are produced by a reputable food container manufacturer for food products only. QRP SEALS STAY PUT. They are designed wide enough that they seat firmly against the roof of any brand Mason jar plastic cap completely underneath the threads and cannot fall out while screwing the lid onto or off the jar. And they are thick enough that they don't wrinkle while tightening. Easy removal for easy clean; clear silicone aids in cleaning inspection. QRP SEALS provide a perfect airtight, anaerobic enclosure while fermenting Kimchi (vegetables) or Kombucha (tea). BONUS: A FREE GIFT of an Our Daily Bread Christian daily devotional is included with each order. If you aren't interested in receiving the booklet, simply send a message when placing your order and request that we withhold the gift. Thanks for your consideration! UPC 682055870175 Color Clear Shape Round Brand Name Quality Reliable Products Item Weight 130 Ounces Closure Type Cap Manufacturer Quality Reliable Products Material Type Silicone Product Style Gallon,Jar,Can Number of Pieces 500