Persol is an Italian luxury eyewear company specializing in sunglasses. The name is derived from "per il sole," which, in Italian, means "for the sun." Formed in 1917 by Giuseppe Ratti, Persol originally catered to pilots and sports drivers. Presently, the company is famous for its durable sports sunglasses. Its trademark is the silver arrow, and several of the company's glasses feature this symbol. Persol was a heavy influence in the production of sunglasses. The company developed the first flexible stem. This flexible stem system is known as the patented Meflecto system and was one of the first spring hinges ever developed for eyewear. Persol was introduced to the United States in 1962. Its first boutique opened on Rodeo Drive in Beverly Hills in 1991. It is currently owned by the Luxottica group. Currently all "plastic" Persol spectacles are made in Italy using cellulose acetate, a hypoallergenic material derived from cotton.