If you go to Eatonbalancing.com (Teds company), he has a section on Y-blocks including tips on installing the rear neoprene seal.You can also do a search on this site for that info. Use the search box at top of page. Here's the link.http://www.eatonbalancing.com/blog/2008/09/10/neoprene-rear-seal-installation-for-the-y-and-others/