WidthScale determines by what factor the width (left-to-right distance) of a
Humanoid is scaled, as well as all accessories not attached to its head. When the description is
Humanoid/ApplyDescription|applied to a Humanoid, this value maps to a “BodyWidthScale”
NumberValue within the Humanoid.
In the image above, three R15 figures whose
HumanoidDescriptions applied with the following WidthScale values (from left-to-right): 0.5, 1.0, 1.5.
articles/HumanoidDescription System, for more information on HumanoidDescriptions
HumanoidDescription/ProportionScale|ProportionScale, which can provide more realistic rig proportions