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What I have is two of each one for the wife and one for myself, all Zumos (2) 590LM, (2) 660, (2) 550 my wife thinks we need to upgrade
every time a new one comes out.
I have the Garmin 665 on my wing and f6b,no trouble for me
2017 ABS Pearl White GoldWing Grand Touring motorcycle
Life is too short to sweat the petty stuff.