I have the rear window out and all the old sealer cleaned off the window and car. So I think I am ready to put the window back in. I'm going to use 3M Windo-Weld but it comes in 1/4 " and 3/8" diameter ribbon. Does anyone know which size is correct? Also it's about 45 degrees today and I was wondering if that was too cold for this intallation?
Thanks for any help.

3/8ths IIRC

Warm the stuff up inside the house first then stick it to the frame and install the window.

Thanks,
I had bought both sizes because I was not sure and live way far from the store. I was just about to flip a coin. So this will be exciting.

Factory was 1/4". But use what you want.
CCLINTAPEDUP

when its done you won't see it anyway

For those who follow.
My rear window and all trim etc. are back together and I should have used the 1/4 " seal material. The thicker 3/8" holds the window away from the lower outside rubber seal just slightly. I was able to use a heat gun and my limited muscles to warm the butyl rubber ribbon, after installation, and compress it by lots of pressing on the window. It now touches the rubber seal but probably won't hold out any water. The car rarely goes out in wet weather so it's good until I want to repaint.

For those who do this remember to use the 1/8" inch thick rubber blocks to hold the bottom of the window off the metal frame. I almost forgot in my haste to get things back together. And don't try to use the rubber blocks that come with the rubber ribbon kit. They are too thick.

The butyl rubber ribbon is a great way to reseal a back window. No mess, little fuss and your done.