Terminal identity and wire range
The 170121-4 is a tin-plated socket from the Commercial MATE-N-LOK series, accepting 14-20 AWG wire with a crimp termination.
Sibling selection: wire gauge and packaging
Within the Commercial MATE-N-LOK series, the 170121-4 (14-20 AWG, bulk) shares its wire range with the 170121-1 (also 14-20 AWG, bulk) but differs in packaging from the 170120-1 (14-20 AWG, tape and reel). The 170148-1 targets 18-24 AWG wire — choose the terminal by the wire gauge in the harness.