I remember doing the first oil change on the ST early last year and thinking the same thing. In fact, I pulled out the old filter, noticed it had the rubber end caps, saw my new one did not and assumed it was a defective part. I jumped in the other car and ran to the nearest Autozone, only to find out Motorcraft stopped putting the rubber caps on. There are other filters that are a direct replacement and still have the end caps, but you are good to use both formats.