"Figure 8" or bi-directional microphones receive sound equally from both the front and back of the element. Most ribbon microphones are of this pattern. In principle they do not respond to sound pressure at all, only to the gradient between front and back; since sound arriving from the side reaches front and back equally there is no gradient and therefore no sensitivity to sound from that direction.
AKG C414 XLII Large-diaphragm Condenser Microphone With 9 Selectable Polar Patterns. Frequency response: 20 to 20000 Hz. Equivalent noise level: 6 dB-A. Sensitivity: 23 mV/Pa. For a detailed Guide to Studio Vocal Mics Under $1000 see https://www.gearank.com/guides/vocal-studio-mics