67 dart windshield lock strip

I got the lock strip from mmpar.com. It's the same shape as the original. The original lock strips shrunk like mad. Mopar had a company make them from another formula of plastic different from the original as a solution to the shrinking problem. I understand people were coming back with new cars in 6 months with shrunken lock strips. When this company stopped making them in the early 70's mmpar said they bought all their stock.