The optical system, construction, and exterior are the same as the EF 75-300 mm f/4-5.6 III USM's. The difference is that it uses a DC motor instead of a USM to drive the AF.
Nice for Price
I bought this lens as an amature, at which time it was very good. However as I've progressed in skill and developed a more discerning eye, the shortcomings of this lens have become limitations. I have found that the only ways to attain a razor-sharp image is studio work (I experimented with it to test its quality and make sure it was really capable of high quality images) or conditions similar to studio work, such as fast shutter speeds, a tripod, or a steady hand. Excellent lens for how much I paid for it.