How do I know which brake pads to buy?

I've got a Cannondale CAA8 which, according to the cannondale website, comes with Cannondale C4 brakes with cartridge pads. The pads are starting to get worn down and I can't seem to find which pad replacements are going to be compatible with the existing ones.
Are all pads compatible with each other, or do I need to find the specific pads for the brake? If the pads are specific then does anyone know which type of block I would have, or anyway of finding out?
Are all pads compatible with each other, or do I need to find the specific pads for the brake? If the pads are specific then does anyone know which type of block I would have, or anyway of finding out?
Neil Pryde Bura SL
Cannondale CAAD8
Cannondale CAAD8
0
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http://www.wiggle.co.uk/p/cycle/7/Kool_ ... 300005952/
05 Spesh Enduro Expert
05 Trek 1000 Custom build
Speedily Singular Thingy
Cannondale CAAD8
or Swissstops if you have money to burn
I've just swapped from koolstops to swissstops there's a massive difference.
One is red the other is green. Oh and £8.
Voodoo Bizango - 2014 - Dead - Hit by a car
Vitus Sentier VRS - 2017