This precision 90° star diagonals feature fully coated mirror, delivering superior image fidelity. It lets you view objects that are at a 90 degree angle from the direction the telescope is pointing, thereby allowing comfortable viewing when the telescope is pointed at, or near, the Zenith (i.e. directly overhead). The resulting image is right side up but will be reversed from left to right. Housings are black - ABS plastic with thumb screw the eyepiece in place.