Our highly rated D21 Eyepieces are matched to 1/100th focal length. Typically 21.6mm, they have a 65 degree AFOV, of course are fully multi-coated. They exhibit NO pin cushion distortion and produce amazing contrast whether used for nightime observations of planets, lunar and deepsky or daytime views in white light and H-a. They are amazing for H-a observations. We feel that the D21s are UNSURPASSED for contrast and sharpness on Ha!
Photo shows our D21 Eyepieces in a Binotron 27 Super System with Filter Switch (not included with D21 Eyepieces)