While the XM 9 20 MSI T is compatible with the HELIX 9 SI MEGA + G3N ... :

The stock xducer for the HELIX 9 SI MEGA + G3N is the XM 9 HW MSI T (which has the Dual Spectrum Low Q 2d)
https://humminbird.johnsonoutdoors.c...130.1577845057

Rickie