I have a 2018 Cannondale Synapse AL SE. It is creaking, and I think it is coming from the steering head. I’ve tried adjusting the preload, and dissembled and greased the headset assembly. The bike is fairly high mileage for its age, 28,000 miles.

I’d like to try new bearings, but I am having a hard time finding an exact match. The factory headset bearings (upper and lower are identical) are marked “TH MR100 1-1/4 45°X45° A8”.

The closest match I’ve found is identical except for the last two letters. “TH MR100 1-1/4 45°X45° CO” What does the last two letters designate? Might that be a lot number or manufacturing facility?