The Volk 28 Diopter B.I.O. Lens offers an improved double aspheric glass design with a "conventional 28D" diameter and field. The Volk 28D Lens provides exceptional resolution and fundus scanning capability. The Volk 28 Diopter BIO Lens is available with standard large holding ring V28LC, small ring V28SC, and for the Argon/Diode Laser VDI28LC. An optional Yellow Filter is also available for these 28 diopter lenses VYF20L. Supplied in lined leather like case.