To get the most out of your Newtonian scope you really need to align or collimate the mirrors.It can take some time getting used to aligning both the secondary and primary mirrors and this short collimator can make it much easier. The short collimator for mirror (reflector) telescopes has a 45 degree plate for easier visual accuracy.Collimation is the alignment of elements inside an optical system like a telescope. Colimating a telescope consists of adjusting the tilt and position of the mirrors and lenses to that the point reaches optimum focus at the point fromwhich the will be viewed (the eyepiece or possibly a camera).colour:blackMaterial:Aluminum alloyPackage Contents:1*Short calibration eyepiece1*boxes1*opp bagOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.