The KPX510 N-BK7 Plano-Convex Lens is an uncoated, 6.35 mm diameter N-BK7 plano-convex lens with an effective focal length of 6.4 mm. It has = λ/2 surface irregularity, 60-40 scratch-dig. N-BK7 is an excellent material for most visible and near infrared applications. It is the most common optical glass, and it provides great performance at a good value.