Whirlwind LITTLE IMP Lo to Hi Impedance Matcher includes Free USA Shipping
Some mixers have 1/4", unbalanced inputs designed for high impedance mics and won't accept standard balanced, low impedance microphones.
This inline transformer with female XLR - 1/4" TS plug is the solution for making that connection.
These are great to bring more volume to the Shaker harmonica mics.