Check the listing for details. Spencer Lens 4mm N.A. 0.66-44x Microscope Objective. Condition: Used, Made in United States. Listed at 19.95 USD. The Spencer Lens 4mm N.A. 0.66-44x Microscope Objective is a high-quality microscope attachment designed for precise and detailed viewing of microorganisms or samples. Made by Spencer Lens in the United States, this microscope objective features a 4mm model with a numerical aperture of 0.66, providing clear and bright images with a magnification range of 66x to 44x. With no custom modifications or bundles included, this microscope objective is a reliable and durable accessory for microscope systems in various industries such as healthcare, lab research, and dental applications.