This is a Rectify Series drop-in speaker system for Athearn Genesis SD70MAc locomotives (newer/current runs). The speaker fits behind the motor replacing the stock speaker/weight. Removing two screws is all that is needed to remove the stock speaker/weight. This system then simply drops-in with small strips of carpet-tape or a touch of adhesive keeping it in place.
 
If you choose to keep the stock weight a RAPO-GMD1-RC1 speaker can be strapped across the decoder.
 
The speaker comes fully assembled and tested.
 
Overall dimensions are: 29mmH x 18mmW x 39mmL