On left - sheath and terminals for 18-14 AWG wire. (NOTE: this sheath will snugly fit 16-12 gauge wire, one 18 gauge wire is a bit loose).
On right - sheath and terminal for 12-14 AWG wire. (NOTE: This sheath is a bit loose on a 10 gauge wire and very loose on a 12 gauge wire. Or use for multiple wires).