i think it is
Looking at my face, I'm no more than six.
Look at the rest of me and I'm 21.
You'll see my twin and me in Las Vegas.
Say my name and you'd be uttering a threat.
What am I?
Abuse me for I will not care.
Curse me when I stray from fair.
Brute force won't put me in my place.
Smooth and even wins the race.
Envy colors where I rest.
No sandy beaches for the best.
What am i ?