Due to factory/genuine spare parts restrictions, an increasing minority of watchmakers in the US are 'independent,' meaning that they choose not to work directly for industry or at a factory service center. One major Swiss watch brand – Rolex – now pre-qualifies independent watchmakers before they provide them with spare parts. This qualification may include, but is not limited to, holding a modern training certificate from one of several reputable schools; having a workshop environment that meets Rolex's standards for cleanliness; using modern equipment; and being a member of the American Watchmakers-Clockmakers Institute. The Omega brand has the same approach. However, the vast majority of modern Swiss brands do not sell parts to independent watchmakers, irrespective of the watchmaker's expertise, training or credentials. This industry policy is thought to enable Swiss manufacturers to maintain tighter quality control of the after-sales service for its watch brands, produce high margins on after sales services (two to four times what an independent watchmaker would ask), and to lower second-hand watchmaking parts on the used and fake market.