20 AWG IDC Receptacle – Wire Gauge Is the Fit
The 20 AWG wire gauge is the hard spec here: this housing accepts exactly 20 AWG wire, so if your harness calls for 18 or 22 AWG, you need a different MTA-156 variant.
Locking Ramp and Polarizing Key – Vibration and Mis-Mate Protection
The locking ramp fastening type gives the mated connection a positive latch – hand-tight should seal it, but the ramp holds under vibration where a friction-only fit would back off. The polarizing key (a molded bump or slot) ensures the receptacle only mates with a header that has the matching keyway, so you don't accidentally plug an 8-position into a 6-position header or mix wire gauges on the same harness. The yellow housing color is a visual cue on the assembly bench – operators can spot the 20 AWG line at a glance.