Any idea where i can get and what type of headset is used.

What fork are going to fit?

if your fitting normal forks, go for a Hope 1.5 reducer headset, just fitted one to my prophet looks well sweet, nicely made with 10mm added clearance on the bottom cup and flush on top.

Rockshox recon

Hope 1.5 reducer headset, looked it up on chainreaction site it said not for cannondale in brackets. Help

Bigsimon

As I said I've just fitted one to my prophet

Speak to hope direct as I did just to confirm your rush will be fine

Where are you based?

If your near chesterfield, I know where you can get it bought and fitted for about £70

i have a hope 1.5 reducer headset in my Rush – it fits fine and does the job great, don't know why CRC would differ? but it definetly works

older Cannondale frames didn't have a very deep recess for the headset cups and hence required shallow fitting cups, all modern Cannondales seem to be fine and most 1.5" headsets should fit OK.

Carbon ones are different

I went the Hope route on my Rush too, very pleased with it. In a different league to what it came fitted with. Think there was an FSA option offered too by LBS.