A "30cm 4-pin JST 2.54mm" cable refers to a cable with a length of 30 centimeters, terminated with a 4-pin JST (Japan Solderless Terminal) connector on one end and bare wires or another connector on the other end. Here's what each part of the specification means: 1. **30cm**: This indicates the length of the cable, which is 30 centimeters. It specifies the physical distance between the two ends of the cable. 2. **4-pin**: This indicates the number of pins in the JST connector. In this case, the connector has four pins, meaning it can carry up to four separate electrical signals or power connections. 3. **JST**: JST is a manufacturer of electrical connectors commonly used in small electronic devices and projects. Their connectors are known for their reliability and ease of use. 4. **2.54mm**: This indicates the pitch of the connector, which is the distance between the centers of adjacent pins. A pitch of 2.54mm (or 0.1 inches) is a common spacing for connectors used in electronics prototyping and DIY projects. These cables are often used for connecting various components in electronic circuits, such as sensors, actuators, LEDs, and microcontrollers. The 4-pin JST connector provides a convenient and secure way to make these connections, especially in applications where frequent disconnection and reconnection are required. The 30cm length provides flexibility in positioning components within the circuit.