The Televue 13mm Nagler Type 6 eyepiece is compact 7-element design which incorporates exotic glasses and coating processes to yield full field pinpoint sharpness.This is a 1.25" barrel design with an 82degree apparent field of view and 12mm of eye relief.The Televue 13mm Nagler Type 6 has blackened lens edges, anti-reflection threads and rubber eyeguards deliver maximum contrast.100% full field visual inspection with TeleVue flat-field test instruments guarantees performance.