Kaika,
Johnny Electron's response is 100% correct.
When AIRMAR constructs any CM599LH, selected transducers are scientifically tested for the "G" designation. There is no difference between any CM599LH or CM599LHG, as these transducer and elements are exactly the same. This transducer testing is required for the transducer setups needed for certain commercial fish finders that have fish sizing capabilities like the FCV1900"G"
I hope this information helps..?
- Deep Blue