TATTLER REUSABLE CANNING LID USAGE Tattler Lids do require a bit of variation from conventional metal lids. Being a two piece combination with a rubber gasket ring, Tattler Lids must remain a bit loose during processing in order for the jar to vent the pressure that has built in the jar during processing. An online customer gave us a very good tip on how tight is 'Just Right'. To get the feel for the correct tightness prior to processing, place the jar on a counter top or other smooth surface, then place your index finger on the lid (do not apply too much pressure while tightening the metal band). Screw the metal band on until the jar begins to spin on the counter top (or other smooth surface). This is the perfect tightness for processing! Are TATTLER Reusable Canning Lids Safe? In one single word, YES! TATTLER Reusable Plastic Canning Lids are manufactured using a plastic compound that is safe for direct contact with food products. We utilize an FDA and USDA approved, food grade product known as Polyoxymethylene Copolymer (POM) or Acetal Copolymer. The rubber rings (gaskets) are made from a food grade nitrile rubber and contain no latex. Neither formulation contains any Bisphenol A (BPA) or phthalates! TATTLER Reusable Plastic Canning Lids are manufactured using a plastic compound that is safe for direct contact with food products.We utilize an FDA and USDA approved, food grade product known as Polyoxymethylene Copolymer (POM) or Acetal Copolymer. The product we use is compliant with applicable FDA regulations for food contact subject to the limitations listed below. This product is formulated using polyacetal base resin that is compliant for use in food contact applications according to (CFR), Title 21, 177.2470. Any additives, that may be present, comply with appropriate, specific FDA Regulations.