Answer:
It is weightless, you can see it. If you put it in a barrel it will make it lighter?
In buckles or lace, they help set the pace. The farther you go, the thinner they grow.
Voiceless it cries,Voiceless it cries, Wingless flutters, Toothless bites, Mouthless mutters.
It can cause deflation of tires when dropped from the rear of spy cars.
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
I am your mother's brother's only brother in law. Who am I?