... :Super wide angle,high index glasses,Fully broadband multi-coating. WA 17mm Telescope eyepieces: Prod. Code :BGWA17Focal Length(mm) :17Lens Structure ... (mm) :16Barrel(in) 11/4Field stop(mm):19.0FEATURES of WA 17mm Telescope eyepieces: Wide angle 65 degrees, high index glasses ... aluminum with a rubber grip ring. Fully broadband multi-coating. WA 17mm Telescope eyepieces