The 1mm Pitch 15 pin 50cm CSI A-Type Ribbon Flexible Flat Cable usually refers to the extremely thin flat cable often found in high-density electronic applications like laptops and cell phones. Each end cable is reinforced with a stiffener to make insertion easier or to provide strain relief.
The stiffener makes the cable slightly thicker. This cable is for the Raspberry Pi ribbon connectors when connecting a peripheral such as an external display, camera, or the AlienSpec Ribbon Connector Breakout Board.
1 x Ribbon Flexible Flat CSI Cable for Raspberry PI (15 Pin, 50 cm)