Watch Back Case Opener For Opening Watch Backs. This is a new watch back case opener. Great for opening watch backs. It measures approximately 4 3/4" (120.6 mm) long. We work hard to update our descriptions and pictures of our merchandise. As part of a process of ongoing innovation by our suppliers, newer versions of the item shown may be shipped before we are able to complete an update. As a result there may be a slight variation in color and design.