The L.E. Wilson Expanding Mandrel Sizing Die is designed to be used on NEW brass cases to prepare the case for the seating operation. Over the past few years we have seen a greater need to run new brass cases over and expanding mandrel to properly prepare them for their first firing. New brass cases are often damaged when shipped in bulk, this die will give you a consistent neck diameter on your cases. With correct neck tension you can expect a more consistent seating depth and shot. Note: Includes one mandrel. Additional mandrels sold separately. FeaturesCut out in die provides an easy view for making sure case aligns and setting up depthInterchangeable Mandrels depending on caliberStandard 7/8ths Reloading PressDie ONLY expands neck to slightly under bullet diameter Stainless Parts for a Long Lasting FinishDurable and AccurateLock nut - thickness is .225" from inside to outermost edge .270" for height and 1.250" total width ODStainless Steel Parts