The strength of the lock comes from being tightened all the way down to the visual stopper. The second outer diameter of the flight, above the small screw thread section is a naked soft plastic that actually gets freshly-scored from the threading on the inner diameter of the shafts at the time that the parts are mated together. This scoring is a custom thread fit on the flight and that is the key to the Double locking mechanism and the strength/lifespan of our system.