This Frontier/Xterra/Pathfinder front 6112 shock utilizes the heavier duty Titan 6112 and our HD lower spring retainer as well as your choice of Eibach spring (silver 500-700lb rate options) Or King (blue and same rate options) The problem with the regular Frontier/Xterra 6112 is that they come with new springs...but are the exact same spring rate as a stock 4wd...very soft and they come unassembled and requre a good spring compressor to put together. If you run a winch or bumper or a heavy rear spring, you will soon find the limits of the regular 6112. These shocks address those issues as the Titan version comes without a sping (saving you the expense of buying another set of springs) and are valved heavier for use with a stiffer coil and more weight (but ride incredibly well) These are the same lenth as the 5100 or any other aftermaket front strut so stock upper amrs work great. You can add our 1.5" billet spacers if you do decide to run SPC or PRG upper arms. Becasue these are designed to be used w stock upper arms, the max height suggested is 2" of lift, if you combine withour spacers and SPC arms, 3.5" lift can be accieved but 3" is best for ride quality (https://www.prgproducts.com/product-page/3-inch-lift-ome-bilstein-5100-extension-kit) If you are comparing these to the Radflos, typically run 50lbs lighter for the same setup. Build time is tyically 1 week.