A set includes four objectives with 4x, 10x, 40x, 100xs magnification. You can use these objectives for classic "dry" observations; also, a 100x objective allows for observations using oil immersion. 40x and 100x models are spring-loaded. A 0.17 mm cover glass is required for observations. Levenhuk MED 900 Plan Achromatic Objectives Set, 4x, 10x, 40xs, 100xs (oil) is designed especially for MED 900 Microscopes. Plan achromatic objectives allow transmitting a quality and sharp picture without spherical and chromatic aberrations. They perfectly correct the field curvature by flattening up to 95% of the field of view. All of the objectives are made for a 160 mm tube length. Body material - metal. Optical design - plan achromatic. Magnification: 4x, 10x, 40x, 100x. Aperture: 4x objective - 0.10, 10x objective - 0.25, 40x objective - 0.65, 100x objective - 1.25. Compatible tube length: 160 mm. Cover glass thickness: 0.17 mm. Spring-loaded frame: 40x and 100x objectives. Oil immersion: 100x objective.