These are T1 (racing) front upper control arms that GM made to help the problem of rubber bushings that "walk" out of the control arm. A known issue. They have a higher durometer rubber in place of the original softer rubber. Durometer is the measure of stiffness or flexibility of the rubber.
I bought these new & used then about 3 months before moving to poly bushings. They are left & right - not interchangeable.
You know if you need them & if yours are good, don't worry about it, you are not braking hard enough to move them.
However, if improved steering response, turn in, holding your alignment settings, are important, these will help even if your original ones look good.
$475 for the pair shipped to lower 48. Add 3% for PayPal.
GM part # Left 12480072
GM part # Right 12480073
The arm and bushing come as one complete unit not a separate bushing and a separate control arm.
The front upper control arms are the only ones that the official GM T1 kit included. They are (mainly) the ones you need to change for better performance, and are compatible with the front lower and the rear (upper/lower) control arms.