The 899ci HD SI Combo comes stock with the XTM 9 SI 180 T...(Compact SI xducer capable of 83kHz/200kHz 2d and 455kHz SI)...
It can be traded (new in the package) for the XHS 9 HDSI 180 T ...(HDSI xducer capable of 83kHz/200kHz 2d and 455kHz/800kHz SI)...
http://www.humminbird.com/Faq.aspx?TaxonomyId=91A1766
I'm not sure about trade in price...(I've heard $50-$70)...
The 899 cannot use the Platinum maps from Navionics...
Rickie