The Kit R rotary optical encoder is suitable for motion feedback applications in which installation space is limited. The scanning unit has a height profile of 3.5 mm, and the 0.5-mm- thick graduation carrier disk is made of lightweight aluminum. The encoder disks have a variety of line counts based on many sizes of outer and inner diameters with each including a reference mark. The aluminum disks are coated to help prevent damage from contamination. The units have a modular design and can be ordered as just the sensor or sensor with a mounting frame.