The HDB-4 is a relay hold down spring used to securely fasten relays in their sockets. Constructed from durable stainless steel, this spring is specifically designed for compatibility with GR, GT, MR, and MT series relay sockets. Its primary function is to maintain a reliable connection by preventing the relay from becoming dislodged due to shock or vibration. The HDB-4 is also RoHS compliant, ensuring it meets required environmental standards for electronic components.