Every drop shackle I have seen for 02-06 trucks are right at 2" shorter than factory,when you consider the shackle is at the very end of the spring you can see yourself how it wouldnt drop the full 2" because of the pivot point. All these shackles are within 1/8th inch of each other and will drop each truck the same,now different trucks will be where a different measurement may occur........things like towing packages,mileage,accessories and more affect how much drop you will get from the shackles.
This is being addressed right now between a member and I who got some Belltech shackles from me and is saying it only dropped his truck 3/4"...........so far he doesnt believe me that all these shackles will drop his truck the same amount,and is telling me I sent the wrong ones to him. The truck,the install,and accessories already on the truck will determine the actual drop,not necessarily the shackle brands. Very seldom does the shackles give you more than 1.5 drop on most trucks.