This is a must for hot running modern 4strokes. My YZF was boling at the really muddy races or in snow sometimes but not anymore since I use the 2.0 radiator caps.
Today's increased water pressure and temperatures require a better seal than stock oil caps can provide. That's why CV4 worked with professional engine builders to develop these new higher pressure radiator caps.
The 2.0 bar pressure version is recommended for Slow to Medium woods or GNCC off-road riding to maintain coolant pressure under extreme load conditions.