20x Larger Viewing Area When Compared To A Standard Or Pocket Ophthalmoscope * Long-lasting Led Illumination Cuts Down On Need For Lamp Replacement * Compatible With All Welch Allyn 3.5 V Power Handles And Wall Transformers * Apertures Small Large Red Free Slit Fixation Target Cobalt Blue * Diopter Range -20 To +25 D * Warranty 1 Year