Here's a coated, achromatic air spaced doublet objective lens for a small telescope. Great for educational purposes. Mounting unscrews and the flint and crown elements can slide out. 50mm clear diameter by 600mm focal length. Great for making a first telescope to see the craters on the moon, etc. Use with PVC or cardboard tubing and one or two of our inexpensive eyepieces. Use this to replace your damaged scope objective. Unused.