This Novoflex unit is a compact precision focusing rail for macro use. Attaches to any tripod head and provides a standard 1/4" thread up top for camera mounting. A turn of the focusing knob moves the camera platform back and forth; tighten it with the other knob. That's all! It's small enough to take almost anywhere, and works well. Gearing is not perfectly smooth, but advances well; cosmetic condition is good, with some paint and finish wear.