Roadrunner rear window ribbon sealer/ gasket

I know this came up before but I cant remember the conclusion.

Does it need 5/16 or 3/8 thick window ribbon?

I think some previously said to try both and see which one works best, but that doesnt see practical..

HELP !

Thanks,

I just used the 5/16th's stuff on my 68 GTX.....mouldings etc all OK

5/16ths

I try to make sure I do not stretch or flatten the butyl strip when I lay it down to ensure uniform contact when laying the glass. That way your seal occurs as the glass comes into contact with the seal. This helps eliminate initial voids and excess working of the glass to meet the butyl strip.

Thanks for the response !

I will pick up a roll tomorrow.

I agree also...5/16".