Your stock KTM or Husq came with a 1.8 bar cap witch will allows for system pressures of about 26.1 pounds per square inch which equals a boiling point of about 290 degrees F.
The Twin Air 2.0 cap ups that to 29.0 pounds per square which moves the boiling point up to 299 degrees F.
It's recommended that all the cooling system hoses be in new or as new shape to handle the increased pressures. Also consider the Samco or Tusk upgrade hoses with the Twin Air Cap.
2016-19 250-450 FC, TC
2017-2019 250-501 FE, FX, TE
2016+ 125-450 SX, SXF
2017+ 125-500 EXC, EXCF