Well he has already answered about the Arbel system, I'm just adding to it.
You're talking about this stock
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It has the power supply for the Arbel system. As it's added below the receiver extension tube, it shouldn't change the ergonomics of the gun while shouldering. Would definitely feel bit rear heavy though.
The working bits of Arbel is integrated on the right side of the receiver.
View attachment 9994
Arbel is really quite ingenious in the way it works.
Typically in any aim assisting smart sights like SMASH or TrackingPoint the scope needs an "active interaction" with the target to get all the data it needs and then it uses algorithms to predict the optimum point to aim. In most cases it happens via an onboard LRF and manually tracking the target. But in case of Arbel everything happens in a passive mode and the system has absolutely no idea what's your target is; it's only interaction is with the gun itself. It works on the age old hit probability problem of small arms where the first shot has a high probability of hitting the target as opposed to subsequent ones because then recoil from the previous shots would be messing with your aim. Just before the first shot is fired it estimates the point of aim by recording all six degrees of freedom using an onboard MEMS based INS. Next time you press the trigger and nothing happenes as the gun's not on the previous vector. So you slightly move the gun while pressing the trigger and as soon as the vector matches the Arbel releases the hammer. This thing loses on extreme precision but as it lacks a LRF you won't be alerting your targets. Also it'd be bit faster.
But given it's high cost it makes no sense for an army that has yet to standardize even an ACOG type optics for its troops.
With 11.5" you'd be limited to only CQB and also given the loud muzzle blast a suppressor would be compulsory so it makes sense only for SpecOps or Naval personnels. A 14.5" is more of a general purpose role suited for the whole infantry.
So 14.5"