  The Simons Observatory (SO) is a suite of telescopes located in the Atacama
Desert in Chile that will make sensitive measurements of the cosmic microwave
background. There are a host of cosmological and astrophysical questions that
SO is forecasted to address. The universal focal-plane modules (UFMs) populate
the four SO telescope receiver focal planes. There are three varieties of UFMs,
each of which contains transition-edge-sensor bolometers observing in two
spectral bands between 30 and 290~GHz. We describe the novel mid-frequency
UFMs, which target two of the six spectral bands at 90 and 150~GHz and are
central to the cosmological goals of SO.
