The Outback Power FLEXware 250 system requires two FW250 enclosures for a single inverter. One FW250 is used for the AC side and one FW250 is used for the DC side. Unlike the FW500 and FW1000, the FW250 does NOT require a mounting plate. The DC enclosure requires one DC breaker for the battery bank and a 2/0 or 4/0 AWG cable for connecting the breaker to the DC input of the inverter. The wire gauge depends upon the DC voltage rating of the inverter. A ground fault protector is required for all installations according to NEC guidelines. If the inverter will be grid-tied, you will also need a FW-SP-250 surge protector. The FLEXware 250 enclosure is constructed of powder-coated aluminum and has been ETL listed. It provides breaker spaces for battery, PV array or PV GFP breakers and mounting locations for AC GFCI outlet, AC breakers and an Input-Output-Bypass Assembly (either the FW-IOB-S-120VAC or the FW-IOB-S-230VAC). The FW250 is rated for indoor use only. Includes: Ground bus bar, DC breaker handle guard, breaker mounting hardware and enclosure mounting hardware.