All of our equipment (except legacy items) is bought new and sold after 2 years of rental use. Before and after each rental we check each lens visually, test it for focus and sharpness, and take pictures with it. We guarantee the glass is clear, the lens works normally, the pictures it takes are sharp. These lenses are used regularly so there will probably be some scuff marks on the barrels, etc. There may be a little internal dust in some lenses (the telescoping zooms are especially known to collect it). If there is any effect on image quality the lens goes off for servicing, otherwise it remains in service.