I bought mine last July. I came with a 38mm motor mount. I called LOC and they said that they are changing it to 38. The old LOC catalog still says 29, but the new order form now says 38. I might fly mine on an H123W or an H148R, I have not decided yet. You can still fly 29mm motors, however, using LOC's 38 to 29mm motor mount adapter, MMA-2.