Choosing Speaker Binding Post Inserts can be confusing. Regardless of the Speaker wire size/gauge you will need a Red Insert & a Black Insert for one Speaker at the wall plate.This applies to standard speakers sold in pairs or Center channel, dual coil is the exception requiring a 4 conductor, and a dual coil is two speakers in one, woofer & two tweeters.Typical the most widely used in-wall rated speaker wire is available in 16 or 14 gauge, 2 conductor & 4 conductor hence the term 16/2 = 16 Gauge 2 Conductor; 16/4 =16 Gauge 4 Conductor; 14/2 = 14 Gauge 2 Conductor; 14/4 = 14 Gauge 4 Conductor.Both 16 & 14 Gauge 2 Conductors are straightforward, Red is (+) Black is (-) = Right Speaker /Channel. Both 16 & 14 Gauge 4 Conductor wire Color code is the same, Red is (+) Black is (-) = Right Speaker/Channel, White is (+) Green is (-) = Left Speaker/Channel.