The manufacturer's website (
Pentax Japan XW-Series Eyepieces), says: "
A Choice of Four Magnifications to Meet Specific Applications - With four different magnifications (7mm, 10mm, 14mm and 20mm) to choose from, the XW series accommodates a wide range of both casual and specialized applications."
The four other eyepieces from both ends of the range - 3.5mm, 5mm, 30mm and 40mm - aren't mentioned.