Actually the MGX was the first Gen 3, then all the rest came out, S, SX, STX, Premier, etc.. the LTX came out in Japan around the same time as the MGX. They all use the same frame and side plates. Apparently some of the gen 3s like the S and Winch use a long spool shaft while others like the STX, Rocket, SX, Premier etc. use the short spool shaft.