I found some re-usable canning lids a couple years ago. These are a plastic flat with a separate rubber ring. You use regular rings to screw them down. All can go in the pressure canner or water bath. I loved them the first year i used them, but I noticed that some of them bowed after I used them, so now some are convexed instead of flat and now won't seal when I use them. Has anybody else seen these or used them in your canning? They are made by the Tattler co. The concept of re using them was why i bought them, but they aren't worth the investment if I can't re-use them. :-?