These air suspension bags are aftermarket ones. They will replace the original rear air springs. Air ride Lift D2500 Air Spring Bag 1/2"npt Suspension Shock two Bellows description： Air Ride Spring Bag is made in steel braided cord reinforced ribs and multi-layer nylon belt cords bonded into the rubber. The all steel top and bottom plates have rolled crimp connections for unmatched durability This front air suspension kit is suitable for Suspension with 1/2" NPT Single Port. Three Mounting Holes at its Bottom. Fits tightly to for your front air suspension strut. Fit for: Universal Air Suspension Bags for Ford F150/F250, for GMC Sierra, for Chevrolet Silverado, for Dodge Ram 1500 2500 3500, etc (Fits for most brand trucks) Specification: Design height: 152mm Min Height: 65mm Max Height: 175mm Weight: 1.6kg Working Stroke: 110mm Loading Cap. at 3.0bar: 2.88 KN Loading Cap. at 7.0bar: 7.25 KN Single Air Port Size: 1/2NPT Install Hole Size: 3/8-16UNC A ir spring bag capacity: 2500LBS