Incredible performance! full field of view at any zoom/magnification. no fringing or aberrations! - Kowa 25-60 Wide Angle Zoom Eyepiece For Kowa 880/770 Series Scopes

This eyepiece is second to none I've seen in 30 years. There are no chromatic aberrations or chromatic fringing around the margins at any magnification level, and the optics are incredibly sharp. This is the largest diameter eyepiece I've ever had the privilege of using on a spotting scope, and the difference is noticeable. Long eye relief is quite easily achievable because of this. Not cheap, but well worth it!!