Laser collimator for easy collimation of your telescope in 1-2 minutes. High-quality, shock-resistant laser, precisely adjusted, with concealed adjustment screws. Precision-machined, hard-anodized socket instead of the less accurate 1¼" chrome socket. Silicone rubber grip protection makes handling easier with gloves. Suitable for Newtonian and SC telescopes, instructions included. "Colli" stands for the abbreviation: Collimation. The term collimation broadly means to align or adjust. Newtonian reflector telescopes are generally considered prone to de-collimation, especially when frequently transported to dark observation sites in the trunk of a car. If you are one of those observers, your laser collimator should be an essential part of your telescope's accessories. With some practice and a little preparation, the telescope can be cleanly re-collimated in one or two minutes.