HELIX 7 SI G2 (and G2N) comes with XNT 9 SI 180 T “Compact SI” xducer ...

The upgrade XHS 9 HDSI 180 T will give somewhat sharper SI images due to the longer SI piezoes ...
https://humminbird.johnsonoutdoors.c...som-transducer

Here is comparison info ...:
HD vs Compact transducer

Rickie