This is a Rectify Series drop-in speaker system for Atlas Classic & early-run Master GP38/40 locomotives. The speaker is a beautiful press-fit between the rear weight and motor mount. No frame/weight/shell modifications are needed! The factory PCB will need to be removed. Decoder installation can by simplified with a Nix Trainz Decoder Buddy and a 21-pin decoder, or you can hard-wire a decoder in.
The speaker comes fully assembled and tested.