The 7.7 FX is basically a Domane 4 with flat bar components. The crankset is Tiagra Hollowtech II, which uses a 24 mm crank axle, just like 105, Ultegra, and Dura-Ace. All current Trek OCLV frames use press-fit BB90 bottom bracket bearings.

If you're still interested, here's a link to ceramic BB90 bearings for Shimano: F1 Ceramic Bearings for Trek BB90/Shimano 10/11 Bottom Bracket (BB)