6p4c RJ11/RJ14 Jack, Cat3, Vertical SMT
The Molex 0855105118 is a 6p4c (RJ11, RJ14) modular jack from the 85510 series, designed for surface-mount termination in a vertical orientation. It carries a Cat3 rating, meaning it's built for voice and low-speed data up to roughly 16 MHz — a common fit for basic telephone lines, fax machines, or legacy PBX equipment. The unshielded construction keeps the cost down and the footprint small, but it won't handle the crosstalk rejection needed for Cat5e or faster Ethernet.
A Cat3 jack like this one is rated for frequencies up to about 16 MHz, while a Cat5e jack pushes past 100 MHz. If you're pulling a new network run for Gigabit Ethernet, this isn't the part — you'd need a shielded or unshielded Cat5e/6 jack. But for a straight replacement on an existing Cat3 voice line, the 0855105118 is a direct pitch and pinout match for any standard 6p4c plug. No re-termination needed, no adapter.