The Mack Turn Signal is a reliable and durable direct replacement for OEM# 1MR578, suitable for multiple Mack truck applications. This 12V standard turn signal features a modular plug-in that allows for easy OEM replacements without the need for rewiring. Sold individually, the Mack Turn Signal is a practical and cost-effective solution for maintaining the safety and functionality of your Mack truck. With its straightforward installation and dependable performance, this turn signal is a must-have for any Mack truck owner.