Hello. I read previous questions regarding fluidmaster valve seal replacement #242. I bought this part because my toilet sometimes doesn't fill back up. However, the valve seal (new one) is different than my old one. The new seal has a nipple extension in the middle. My old seal is hollow in the middle? Do I need to do something with the new one? Did I buy the wrong part? There is no way to fit he new part in the mechanism. Thanks.