I don't know. The Wilderness Giles sling is a superb product for many platforms, inlcuding the Remington 870, AR variants, etc. It is the best Steyr AUG sling out there. I own three of them for the 870, AR, and AUG. Ralph and Joan stand behind their work like no one else, too.
Haven't seen the Urban ERT sling in person yet. I like to try slings before I buy one. Too many producers are putting too many gimmicks on them, mnaking them too complicated.