The SB175 GREY plug will ONLY mate with other GREY SB175 plugs. SB175 RED and GRAY plug WILL NOT MATE TOGETHER as they are KEYED differently . The SB175 will not mate with a SB350 plug or SB50 smaller plug. The SB175 plug of the same color will mate even with different wire sizes as the actual contacts are the same( example-  4 awg Anderson Contacts will mate with 1/0 contacts as long as the Housings are the same. Grey to Grey, Red to Red. NOT GREY TO RED. NOT SB175 TO SB350 SB175 TO SB175 ONLY.  THE WIRE WE USE TO BUILD WITH IS 100 % COPPER   NOT THE CHEAP (CCA WIRE)-COPPER CLAD ALUMINUM) 1/0 GAUGE SAE WELDING CABLE • Resists abrasion, cut, tear, flame, grease, oil  and water • National Electrical Code article  630 electric welders • Rated for 600V • RoHS Compliant EDPM jacket and paper separator Highly flexible Class K 30 gauge copper • VW-1 Flame test as per UL2556  Suitable for battery cable per the UL558 & UL583 -50°C to +105°C (-58°F to 221°F)   • Made in the USA  THE ANDERSON CONNECTORS ARE 100% AUTHENTIC  NOT THE KNOCK OFF CHINA ONES. THE CABLE LUGS ARE ELECTRODE PLATED  MADE OF T2 RED COPPER 600V