I know that idea of a reusable canning lid is popular, because of the expense of the flat metal lids, but I was skeptical. Previous versions of reusable lids often did not seal well and often did not maintain a seal.
I found the lids on the Ball/Kerr web site, but there are other companies that make them too. It it clearly stated on the box that they are for storage in the refrigerator and freezer and for dry foods. They do not seal jars for shelf stable canned goods.
For jars to form the vacuum seal required to keep the food safe inside the jar, there must be away to let the air out of the jar as it is processing. The two piece band and flat lid is designed for this purpose. Steam escapes as the jar heats, the band holds the lid in place and when the steam is gone the sealing compound glues the lid to the jar. The other important factor is having the correct head space for the food being canned.
These lids are not to be used to processed canned food for shelf stability. They can be use to store opened canned food in the refrigerator, making foods that are stored in the refrigerator, freezing foods, and storing dried foods.
According to some blogs that I read, some brands of the plastic lids have a gasket in them, which can help reduce leakage if the jars tip over in the refrigerator. Another blog suggested saving money by reusing screw-band lids from store bought foods instead of buying these.
This link will take you to the Ball/Kerr website page about lids.
Canning Lids 101