This is an RCBS Cowboy Carbide 3 Die Set in 45 Colt - 45 Schofield calibers. RCBS Cowboy Dies are built to slightly different dimensions than their regular dies to allow optimum sizing expanding, seating and crimping needed to load great lead bullet ammo for Cowboy Action shooters of lever-action rifles and single-action revolvers. Uses shell holders RCBS #20 or Lyman #13.