Vinyl shrinks and expands with cold and heat, respectively. I found a product that's made entirely of rubber. No more shrinking, cracking and no more replacing. I pulled out that old crap vinyl and replaced it with an all rubber trim. There are two sizes to pick, 5/8" and 7/8" width. You purchase the trim by the foot. The company will send out samples of each, if you wish. The 7/8" fit best for our 2017 RW, #70-3979-240. Color is black. It took a little nudging to get into place, but it looks perfect once in. I put a couple dabs of RTV silicone adhesive on both ends to seal. Company will send a catalog if you request. There are slide out, window, door, compartment seals, plus much more. Toll free: 800-230-5897 or
website:
www.rv.steelerubber.com With the COVID19 problems affecting us all, the company is operating, but their sales staffs are working from home, so be patient.