These are two different Rectify Series drop-in speaker systems for current-run Athearn Genesis and RTR locomotives that come with the "dual-cube" speaker or weight. The speaker uses the factory mounting screws to mount to the plate or into the locomotive and no modifications are needed to replace the factory speaker or weight.
The UNI1 will drop-in to the current RTR SD40-2s mounting plate, but I do make a specific speaker for these that replaces the stock plate and sounds a touch bigger: https://www.scalesoundsystems.com/product-page/athearn-rtr-universal-sd39-40-2-current-run
The UNI2 will drop-in to the weight of the current Genesis GP38-50s, but I do make a specific speaker for these that replaces the stock weight and sounds a touch bigger: https://www.scalesoundsystems.com/product-page/athearn-genesis-gp38-39-40-49-50
The speakers come fully assembled and tested.
UNI1: 13mmH x 17mmW x 38mmL
UNI2: 13mmH x 13mmW x 34mmL