While competitors have changed the orientation of the motor, their products' appearance, construction materials and other features over the years, Kirby has remained with its original design, materials and functionality with enhancements added to aid in its operation and durability. The company changes the appearance of the cleaner with revised color schemes and introduces new model names while keeping the core technology intact. Used machines are widely available for sale internationally. Because the attachments and appearance items are interchangeable between generations, some machines can be found consisting of parts from multiple models. Machines built in the 1930s, 40s, 50s and 60s are still in operation worldwide and can be completely repaired or rebuilt with widely available parts from the factory.