Trail.WidthScale
This property is a NumberSequence that scales the width of the trail over the course of its lifetime. Values can range between 0 and 1, acting as a multiplier on the distance between the trail's attachments. For example, if the trail's attachments are 2 stud's apart and the value of this property is 0.5, the trail's width will be 1 stud and the trail will be centered between the two attachments.