Not quite the worst, but spend your money elsewhere
While not an E2X fan by any standard, I can see the need for this kind of kit. Estes has this kind of kit aimed squarely at a first time flyer who wants to experience some building along with the thrill of flight in one weekend. This kit is so poorly designed that it will likely only give the buyer a sense of frustration. The biggest issue here isn't the largely plastic construction, but the inability for the 13mm engines to fit without exerting possibly fatal force onto the body tube. I plan to run a file along the inside of the plastic end cap to see if I can remove enough excess material to fit the engine in, but that's WAY more than you should have to do to get a kids rocket flying.