The Cartier Ballon Bleu is perhaps the most commercially successful watch design Cartier has produced in the twenty-first century, introduced in 2007 with a design language that is immediately recognizable and entirely its own. The defining feature is the large, convex crown guard — a smooth dome housing the winding crown that integrates seamlessly into the case flank, giving the watch its balloon-like, rounded silhouette and its name. The sapphire synthetic cabochon set into the crown adds a jewel-like accent characteristic of Cartier's house style. The Ballon Bleu is available in an extraordinary range of sizes from 28 mm to 46 mm, in steel, yellow gold, rose gold, white gold, and two-tone configurations, with quartz and automatic movement options and numerous dial finishes. Pre-owned Ballon Bleu references are among the most liquid and widely traded Cartier watches on the secondary market, with the 36 mm and 42 mm steel automatics representing the most popular configurations. Diamond-set versions and those with gem-set dials command significant premiums. The Ballon Bleu's fluid design has proven remarkably enduring for a contemporary creation. DeMesy & Co. in Dallas has been a trusted source for pre-owned Ballon Bleu de Cartier watches since the model's introduction.