I wanted to upgrade the 40x DIN achromatic objective that came with my AmScope microscope and knew that Nikon has a reputation as one of the top four makers of premium microscopes. After seeing numerous E Plan objectives available at reasonable prices on the second-hand market, I did some background checking and learned that Nikon's E series is considered their "entry" or "educational" line. That detail, combined with their abundant second-hand availability (why were so many people getting rid of them, and so cheaply?), made me slightly wary despite the Plan designation and the Nikon brand, but I decided to take a chance and buy one. Wow, great decision! Even though the AmScope 40x achromat gives surprisingly fine images, this Nikon E Plan is visibly better, revealing subtle and tiny details that I hadn't noticed before. As a bonus, it's also parfocal with the AmScope achromats, avoiding any need to refocus when switching from the AmScope 10x objective. I should add that the one I received, even though listed as "used," was in like-new condition. I'll be using the 40x setting a lot more with this one!