I have a complete 18" stainless wilson arms barrel with m4 flat top upper that is brand new and has never been shot. I would like to trade for a 16" complete upper in good shape, i would like a flat top but i could settle for a carry handle. It has a vortex muzzel break, free float hand tube, harris bi pod, and low profile gas block. It is brand new in PERFECT shape and has never been shot. If you are interested i will send pics.