Here's some info on the RAM parts and Garmin / RAM cradles you need for mounting a StreetPilot 2610 on "my" mount, with part numbers and pics. I just sent the info in a mail message to somebody, but it thought it might be useful if I posted it here, for everybody to see.
The 1" ball comes with the mount.
What else do you need?
1) A RAM arm
RAM-B-201A Double socket short arm for 1" size ball, 1 3/4" centres
2) A cradle to hold the unit
The Garmin and RAM cradles both have their pros and cons. Personally I prefer the RAM cradle. It has a firmer grip on the unit, and it is easier to take the unit out.
The Garmin cradle is smaller and it has a security screw that offers a bit of theft protection. But that means a bit more of an effort for you to take the unit off too.
2a) For the Garmin motorcycle mount:
* RAM-B-202 2 1/2" Diameter Base with 1" Ball and screw.
* 10495-01 Garmin motorcycle mount
OR
2b) For the RAM motorcycle mount:
* RAM-B-238 Diamond base with ball 1"
* RAM-HOL-GA9U NPI RAM Plastic StreetPilot 2610/2620/2650 Unit Cradle
3) A cable
Here you have the choice between the motorcycle cable and the car cable.
3a) 10495-02 Power/Audio Cable (bare wire power cable with 2.5mm audio jack)
You can get the "ready made" motorcycle cable that has bare ends for power, an inline fuse and a 2.5mm audio jack.
OR
3b) 10477-01 Cigarette lighter adapter w/speaker
Cut off and have power and audio connections under the tank. You'll have to add an inline fuse (0.5 A) yourself.
That's about it. The choice is up to you. What I'm using is 1) + 2b) + 3b).
Cheers,
Michel