Silicone/rubber Apple Watch straps provide a lot of grip and stay in place when you exercise with your Apple Watch. These straps are also easy to clean. Silicone or rubber straps are water-resistant, so you can leave them on while you swim or shower. When choosing a silicone or rubber strap, make sure you choose the right size. The Apple Watch 38, 40, 41, and 42mm straps fit on each of these sizes. The Apple Watch 44, 45, 46, and 49mm straps fit on each of those sizes.