The Moab shock from Cogent Dynamics will change how you feel about your GEN 3 KLR650. You may like it now, maybe even like it a lot, but you will absolutely fall in love with it once you mount up a Moab shock.
Spring duties are handled by a custom spring available in either Standard or Heavy-Duty weights. The Standard spring will be fine if you are under 250 pounds and don't ride with luggage or passengers often. Ride heavily loaded or with a passenger regularly and you will probably want the Heavy-Duty spring.
There is very limited manual preload adjustment access on the Gen 3 KLR650 without removing the shock. Therefore, the addition of the Remote Preload adjuster gives you the convenience of optimizing your rear suspension spring preload for quick leveling (load compensation) of your bike to accommodate a passenger, luggage or just to change ride characteristics based on your preferences. The adjustment which would normally require reaching the shock in your bike to turn a threaded collar using a tool can be easily adjusted by twisting a remote knob which uses the convenience of hydraulics to change the spring preload up to 100% (9 mm total range of preload change).
There is a mounting conflict for the Remote Preload adjuster with the Happy Trails and T-REX crash bars.