I use two of these on the front of my tadpole trike with 406mm diameter wheels. I tried the 20 X 1-18 to 1-14 Schrader valve version first. The tube crossection was 30 mm minimum and the tube accordianed inside the tire. A bike mechanic warned me that a tube in such condition would have a very short life. When I installed the first one there were two pinch punctures. These tubes are made of thinner rubber than regular bike tubes. My wheels are double walled and have recessed holes for spoke nuts. The tubes ruptured when inflated to 95 psi because they were cut by the edges of the holes. Wide wheel liners fixed this by covering up the holes.
The Presta valve version has a 28 mm crossection and smaller overall diameter. These worked fine (with the new wheel liners) and installed much easier. One still must take care to avoid pinch flats with 406 diameter rims and tight tire beads.
We agree that it is important to pick the correct size tubes. It is better to use a slightly narrower tube so that it will not fold or twist inside of the tire. Be careful, as well, not to pinch the tube under the bead of the tire - this is easier to do with a correctly sized tube.
It is also important to use rim liners (aka rim strips) to protect your tubes from either the holes for recessed spokes (as above), or the protruding ends of spokes with a single-wall rim.
I bought these tubes for my new Kenda Kwest tires I put on my folding bike. The tires take up to 100 psi so I thought new tibes were advisable. So far I have no complaints about the Quality Tubes which are made by Kenda also.