Raymond,

Sorry I can not help you on that one, because I am not very familiar with the Pentax line. I do know that they are a very good pair of binoculars, but not sure on how they compare with the Nikons. As for the Nikon eyepiece, it is not a common problem. I have heard of many different brands have problems of some kind at one point or another, such as the Steiner Predators and the eyecup falling off.

Jon Jackoviak
The Optic Zone
www.theopticzone.com
[email protected]