In May 1985, designers started work on the F1 project. In late 1985, designers presented the first exterior study models to F1 management, featuring a sports car-like design with a low-slung hood and narrow front profile. By 1986, the sedan used a three-box design with an upright stance, more prominent grille, and a two-tone body. Extensive modeling and wind tunnel tests resulted in a low drag coefficient for a conventional production vehicle of the time ("C""d" 0.29). For the passenger cabin, the materials-selection tests evaluated 24 different kinds of wood and multiple types of leather for two years before settling on specific trim combinations. By 1986, the Lexus marque was created to support the launch of the flagship sedan, and the vehicle became known as the Lexus LS. Following eight design reviews, subsequent revisions, concept approval in February 1987, and over US$1 billion in development expenses, the final design for the production Lexus LS 400 (chassis code UCF10) was frozen in May 1987 with design patents filed on 20 February 1987 and 13 May 1987.