Connectors are sold with quality connector housings, terminals  .  Wire used is mil-spec tefzel wire, common in aviation & motorsports, which is made of tinned copper strands.  This allows for better corrosion resistance, excellent conductivity & makes repairing/soldering much easier.  The wire has a Teflon like insulation that is extremely durable compared to standard automotive grade wire.  Most connector pigtails sold by others do not offer these properties