These are two different Rectify Series drop-in speaker systems designed to mount in what would be the cab-end of Athearn Genesis B-Units.
 
For B-units that shipped using an A-unit frame, the B-Bomb seats in place of where the cab interior would have been. The speaker features pins that mount into the frame holes and a touch of adhesive secures the system. No modifications are required. Use alone or together with the AHGS-F700-RC1 (pre-sound frame) or AHGS-F701-RC1 (sound-ready frame) for an even bigger sound!
 
If your B-unit locomotive has a B-unit frame with circular recesses for speakers at both ends, the BOMB will not work. For these frames you will need the AHGS-B701-RC1 speaker that is designed to fit the "front" position of these B-unit frames. It is bascially a slightly shortened AHGS-F701 speaker so that the dual shell mounting-pads will clear. Use alone or together with the AHGS-F700-RC1 (pre-sound frame) or AHGS-F701-RC1 (sound-ready frame) for an even bigger sound!
 
Both systems feature Diapasonic Tuning™, which allows the lower frequencies to accurately develop and resonate, clears the midrange of excess resonance and tunes the upper-mid/high response.
 
The speakers come fully assembled and tested.
 
Dimensions are:
AHGS-BOMB: 14mmH x 26mmW x 42mmL
AHGS-B701: 14mmH x 28mmW x 34.5mmL