I am impressed with the Thunder Tigers on the new students planes. Easy to adjust like the OS engines and good smooth power. The Super Tigers that I have come across are finicky to adjust and to try and keep running. They also are not finished very well. The carb barrel has suddenly jammed leaving the throttle frozen in one position. I have also seen this happen on their 60 size engines. My first choice is the OS AX but if you are looking to save a few dollars then I would go with the Thunder Tiger. ps. Get the 46 size over the 40 size, same weight but more usable power and pretty much the same price. [8D]