...

unique features you are looking for. A 6-element fully multi-coated optical design, the X-Cel utilizes extra low dispersion (ED) glass on its most highly curved surfaces, to minimize chromatic aberration that can hinder sharp planetary views. With a wide 55° apparent field of view, and a large 25mm clear aperture the X-Cel is one of the most comfortable eyepieces to use. Every X-Cel eyepiece is parfocal with each other, meaning little or no focusing is needed when changing from low to high power. The X-Cel comes with soft rubber eyecups and a durable plastic case. In addition, if you are an eyeglass wearer, you will enjoy the 20mm eye relief available on each of the X-Cel focal lengths. Threaded barrels accept 1-1/4" Celestron thread-in filters.

...

is a 6-element, fully multicoated optical design with extra low dispersion (ED) glass on the most highly curved surfaces to minimize chromatic aberration which hinders sharp planetary viewing.  With a wide 55° apparent field of view and a large 25mm clear aperture, the X-Cel 5.0mm is a comfortable eyepiece to use.  Eye relief is a very respectable 20mm, so even if you wear glasses you'll enjoy the whole view.  And of course, the X-Cel 5.0mm eyepiece is threaded to accept Celestron's collection of 1.25" eyepiece filters. The X-Cel 5.0mm eyepiece is parfocal with others of the X-Cel series, meaning little or no focusing is needed when changing eyepieces within the collection.