I purchased an assembled HardRock-50 kit from the ARRL annual auction in the fall of 2015. The kit (S/N 1251) build was documented and described in an ARRL equipment test in the December issue of QST magazine titled “HobbyPCB HardRock-50 160-6 Meter 50 W Amplifier Kit” by Phil Salas, AD5X. The article contains a complete description of the amplifier including performance test results for the completed kit. The amplifier included the installed optional internal automatic antenna tuner option. Installation and operation/performance of the tuner is detailed in an equipment test article in the March 2015 QST magazine also by Phil Salas, AD5X. I have enjoyed using the amplifier with my KX3 and can echo Phil's observations made in the two articles. This past summer, I purchased the optional KX2/KX3 to Hardrock-50 Interface but haven't used the amplifier with the interface. I am selling the Hardrock-50 amplifier, internal automatic tuner and interface (along with interconnection cables to connect to an Elecraft KX2/KX3 for $475 + actual cost of packing, shipping and insurance (if desired). Payment by PayPal is preferred. Send all serious inquiries to email@example.com and Thank you for you interest. Bill Modlin, AK4PI.