The 28-lens 4-bar retinoscopy rack is very useful when screening children and on-site patients. Lens Selection for SRS428 Concave and Convex Lenses – 0.50D, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 5.00, 6.00, 7.00, 8.00, 10.00, 13.00D