it's the same mcmaster-carr epdm as what was being discussed, just in a smaller sizing that's compatible with the stock fittings. direct link to the 5/16 x 7/16 can be found here.Whatever tubing you're using, I'm pretty sure it's some other type of rubber/plastic. It appears from the photos like it's seemed, and EPDM is seamless. All commonly available EPDM should also be marked as such unless, like I assume EK did, you contract with the factory to get it without branding.
Edit: Where did you source the tubing?