These are simply the best eyepieces made.
Think of all the heavily advertised eyepieces on the market. NONE have all 3 of the important features required to be considered the best.
High Contrast and Resolution, Eye Relief and Wide Field of View.
All of the "Big Name" eyepieces have one or two features but never all 3. Except PENTAX. You can get the famous brands or the best.
The series has expanded from seven focal lengths to eight from 3.5 mm to 40 mm. The XW series features a wide apparent angle of view (70 degrees), JIS Class 4 weatherproof construction and a long eye relief (20 mm). We have tested them and the eye lenses are very wide and have a huge "sweetspot", unlike some wide field eyepieces. The new design uses ED Lanthanum glass and the world's best PENTAX-SMC multilayer coatings.
PENTAX offers the XW 30 and XW 40 eyepieces for planetary observations. Each eyepiece is compatible with the PENTAX PF-80ED, PF-80EDA and PF-100ED spotting scopes as well as a wide range of telescopes. Engineered using advanced computer simulation design technology, both eyepieces feature a 70-degree field of view, long eye relief, and the superior, high-performance glass elements and optics PENTAX is known for. Unsurpassed in their optical performance and quality, these eyepieces provide the ultimate in image sharpness and contrast.