Beside the fact that these ones are the cheapest 82° eyepieces, they're of good quality. Even with the 7 mm model has a relatively large, 22 mm eye lens and 15 mm eye relief.
The field of view is well corrected, the image is sharp even at the edges. The longer focal length eyepieces are more dependant on the errors of the telescope optics, therefore a coma corrector is recommended for fast newtonian telescopes.
All air-glass surfaces are fully multi coated, resulting in high light transmission. The eyepieces are excellent for deep-sky observation as well.
The larger field of view comes with many advantages. For example, the 15 mm model provides the same field of view as a 25 mm standard Plossl, but at a much higher magnification, resulting in darker sky background. The wide field comes handy also when faint stars need to be found in the field. According to our tests, approximately 0,5 mag fainter stars were visible with this eyepieces.
The eye to eyelens distance can be adjusted by turning the ring on the eyepiece. The rubber eyecup can also be removed.
The 7 mm and 15 mm models fit into the standard 1.25" focusers, while the 23 mm require 2" focuser.