How to get the V value from Hair?

So im trying to create a tubes effect for the color and i cant get the V value to map a texture on the widith of each hairs in a hair groom from the hair atributes expression node.
I tried getting the U and using a custom rotator to rotate the value and it doesn’t work, same if it try to use Length, any ideas anyone?

This is just a thing that V-Ray logs.
The value on the right is zero which means this stage is not adding to the render time.

“This is just a thing that V-Ray logs.”
Are u refering to the V attritube from the Hair Atributes Expression node?
So if it were to be mapped in 2D view it would have only height and no widith?

@mickeal_alex I didn’t understand your question.

I dont understang youre first answer, how do i get the V value for the hair to apply a tube texture?