3 Watch Case Knives Jewelers Watchmakers Opener Tools. This is a new set of 3 watch back case openers. Great for removing pressed on backs on all watches. These will open the most difficult watch backs. You receive: One case opener that measures approximately 5 1/4" x 3/8" (133.3 x 9.5 mm). One case opener that measures approximately 5 1/4" x 5/8" (133.3 x 16 mm). One case knife that measures approximately 6 1/4" (159 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.