Gambit marked the first use of next-generation launch vehicle systems as Convair and Lockheed, the builders of the Atlas-Agena booster, began introducing improved, standardized launchers to replace the multitude of customized variants used up to 1963, which caused endless mix ups, poor reliability, and mission failures. This followed a recommendation by the Lewis Spaceflight Center in Cleveland, Ohio that Atlas and Agena switch to one standard configuration for both NASA and Air Force launches, with uniform testing and checkout procedures, as well as improved materials and fabrication processes for the various hardware components in the boosters. The Agena D, a standardized Agena B, arrived first, with the uprated Atlas SLV-3 taking another year to fly. The first eight Gambits flown still used custom-modified Atlas D ICBM cores, with Gambit 4010 in August 1964 being the first use of the SLV-3. Afterwards, all GAMBIT used SLV-3s aside from 4013, which used the last old-style Atlas remaining in the inventory.