Canning rings exist only to hold sealing lids in position. They need to be manipulated over a wide range of temperatures so they spin on easily. These lids have a different job. They're made to tighter tolerances of soft aluminum. You'll read reviews claiming they don't fit standard canning jars—ignore them. Line up the threads and screw them on. They fit snugly, as they should to do their job, but they fit perfectly. I've even put a couple on plastic almond butter jars for use where vulnerability to bonks and falls makes glass problematic. Again, perfect air-tight fit.These arrived nicely packaged, individually wrapped, the light wires coiled compactly. Common sense and reasonable motor skills expands those coils into long springs that go into (and incidentally back out of) jars without complaint. It's too bad the switch is inside the sealed jar, but that's necessary for waterproofness. I never leave them outside in wet weather, but even dew or damp air could compromise the switch if it were exposed. Dry cells are generic NiMH, nominally 600mAh, so they'll need periodic replacement as their capacity diminishes.All in all, these are a very well-made version of a cheerful decorative flourish, a relative bargain if that's what you're looking for, though almost any other light source is less expensive in lumens/$ terms. I quite enjoy them in a variety of settings.Oh, I almost forgot: someone complained the wire hanging bails were difficult to manipulate. Balderdash. I bent each joining hook to 100° (instead of 90°) just to make the connection a bit more secure. Bending was effortless. Connection was a trifle fiddly because of the increased angle but easily accomplished with fingernails; I could as easily have installed the bails and then bent the hooks—the steel is that soft . Install with the hook facing down.