For rubber, the spring bar principle stays the same. A NATO, on the other hand, slides between the spring bars, once they’re back in place, and the case: no tool once the bars are fitted, but the strap adds thickness under the watch. To compare how a diver looks on rubber, on a NATO or on a steel bracelet, the thread (originally written in Spanish) “My Submariner on rubber, NATO or bracelet?” shows the difference well.