Free ShopRunner membership with select AMEX credit cards

If you have an American Express credit card, you may be eligible for a free ongoing membership to the Shoprunner service. Shoprunner gets you free 2-day shipping on select retailers on select products. It was created as an alternative to Amazon Prime. You can activate this either from the Shoprunner website or the American Express website.

PS: I don’t know which AMEX credit cards qualify for this offer, or if this is for all cardmembers or some.