HOSA CMP-105 Mono Interconnect, 1/4 in TS to 3.5 mm TRS, 5 ft

This Hosa Stereo Mini Male to 1/4" Mono Male Cable is a 5' long cable that can be used to "sum" stereo to mono in one direction, or to apply a mono signal equally to the left and right in the other direction.  A common use for this cable is to patch the headphone output on a phone or computer into a single powered speaker or a single mixer channel, where you need both sides of the stereo image that's leaving the headphone output to combine into a single, mono signal before entering your mono speaker or mixer channel.

Yep.