The Boeing Company Phantom Works has developed three different prototype photovoltaic concentrator arrays since March 2007. Identified as Prototype A, B and C, the experimentally proven technical characteristics of each design are presented.The concentrator designs utilize a 1 cm 2 multi-junction solar cell assembly in conjunction with SMS non-imaging optical designs [1, 2] manufactured with low-cost mass-producible technologies. Prototype A is an on-axis XR optical concentrator with a 733x geometrical concentration demonstrating a ± 1.73° acceptance angle and 23.7% conversion efficiency. Prototype B is an off-axis free-form XR optical concentrator with a 810x geometrical concentration demonstrating a ± 1.32° acceptance angle and 25.3% conversion efficiency. Prototype C is the most recent off-axis free-form XR optical concentrator with a 801x geometrical concentration and a theoretical ±1.80° acceptance angle demonstrating a conversion efficiency greater than 27.0%. Prototype C is also the basis for the Boeing Proof of Design (POD) module, demonstrating an acceptance angle of ±1.48° and a conversion efficiency of 29.4% (as of May 8, 2009). Manufacturability has been paramount during the design process, resulting in high performance concentrating photovoltaic modules using production quality components.