Several of the tenax fastners on my 348 Spider top cover were damaged and would not stay fastened. I found an inexpensive source of these little button fastners. The source is American Trim and Upholstery Supply. The web page is http://www.atrim.com/Page109.html . They are so cheap that the best idea is to just replace all of them. Be sure to order the key tool that is used to tighten them. With this tool is is a very simple process to unscrew the old ones and screw on the new ones. This source also has the posts that the fastners attach to. But the posts rarely get damaged.