The Sheen tab is part of the V-Ray Material parameters.
Parameters
Color – Specifies the color of the sheen layer.
Glossiness – Controls the sharpness of reflections. A value of 1.0 means all of the light reaches the diffuse color, and when the value is smaller, the cloth material looks glossier. See the Sheen Glossiness example below.
Example: Sheen Glossiness
This example shows how changing the glossiness parameter of the sheen layer affects the material. The Amount is set to its default value of 1.
Glossiness = 0.1
Glossiness = 0.3
Glossiness = 0.6
Glossiness = 0.8
Glossiness = 0.9
0.1
0.9