"The Tele Vue 12mm Type 4 Nagler eyepiece provides excellent contrast, reduced pincushion, more true field, and longer eye-relief. With added eye-relief, the click-stop Instadjust eyeguard helps maintain proper eye distance and centration"
That's the official blurb
What they dont add is that this is a very versatile eyepiece can be used in 1.25 format or 2 inch as well just by using either format.
Added bonus the 1.25mm piece screws out and it becomes a 24mm 2 inch wide eyepiece.
Similar to a Baader Hyperion but with the quality of Televue.
I have owned this since new (8 years) and it provided me with wonderful views of the sky and planets moon etc. Since I am moving more towards Astrophotgraphy I have to let this go. It is in immaculate condition, Still have the box, caps and instructions.
Yours for $340 ONO posted Reasonable to negotiation (no paypal ever!)