I installed, a few years ago, aftermarket ones and had to use glue to hold it in shape.
The seals I bought recently this spring from Mikes were the one attaching to the outside t-top rails; sealing to the top of the windows.
In original GM packaging.
As with many GM parts, there is a left and right, but very similar.
I didn't use any adhesive.
He has a variety of original / NOS parts.
You have to ask - he often assumes those calling are wanting the less expensive reproduction parts.