The Xtreme (waterfowl model) has the typical shims for cast and drop. However, unlike the wood A400 models or older models such as the Xtrema2, SBEII, etc., which all have the shims stacked between the stock and action at the wrist the Xtreme has a split stock. Which requires complete disassembly of the stock and the K/O system, which without any instruction provided takes some figuring the first time through. Once figured out it's a relatively easy process and well worth the effort as these are excellent waterfowling guns.