The PS-640 is part of our PS range of sealed lead acid batteries (often referred to as VRLA) which have been specifically designed for general purpose and standby applications. The 6 V, 4.5 Ah battery offers excellent performance in a wide range of applications including security and fire systems, medical services, emergency lighting and UPS systems. All Power-Sonic® batteries are subject to stringent quality controls through every step of the manufacturing process ensuring both consistency and reliability.