No talk about sucking the air out of jars, and having the rubber seal of the lid "sealing" on to the glass top just like canning, only they are reusable. I seal up rice, sugar, cereals, beans, crackers. Basically any dry food except flour. It keeps bugs out for sure. My DH made me one 40 yrs ago, but I thought there was one on the market to seal food in jars.