Let’s take a look at the TrailFX gizmo.

Under properties, Length determines the time it takes for the tail to catch up to the gizmo after it stops moving. Width changes how wide the trail is, in meters.

You can even paint the trail by changing the start color and the end color. These numbers represent RGB values from zero to one.

In the Preset drop down box, you can choose between Simple Trail and Tapered Trail. Simple has the same width along the entire trail, while Tapered becomes more narrow at the end.