u/DisciplineOk1120

Just bought a used 2019 Endurace CF SL Disc 8.0 Di2 Large ultegra. I plan to fly with the bike and am looking for what tool I need to remove the rotors for travel. It is a center lock rotor. Parktool has 4 varieties of center lock tools.

I just bought a used 2019 Endurace CF SL Disc 8.0 Di2 Large. Love the bike so far but I have a question.

On the downtube in between the 2 threaded holes to put a water bottle holder there is a circular area punched out with a plastic insert in it. What is this and does it have a function?