These power distribution blocks are Listed to the power distribution block Standard UL 1953. They contain the same features and characteristics as the non-listed blocks however, these have spacing's that are suitable for installations in most industrial control panel feeder and branch circuits, HVAC systems and Wireways (with optional cover sold separately). They are available in one, two or three-pole configurations. An adder is also available with optional end barrier (sold separately), to allow user customized configurations.