I have a Heizer Defense interchangable Barrel single shot, double action pocket gun. There are three different barrels which fire four different calibers, .410/.45 Colt, .223 and 7.62X39. It also includes a neat zipper bag I had to beg for from Heizer, a holster and the Factory Box and Implements. If you were to buy the gun with one barrel and the other two barrels it would cost about 1000.00 retail.