Both upper and lower are M6 threads, compatible for Bergeon 5500A/5500C Great for closing your watch case after resizing or repair job. You can press the tool by tightening the top handle, which means you have full control over the pressure used. It is easy to break the watch with other tools while you feel it prefect to close case with our tool. Face down configuration means the repair person sees the case back being closed.Specification:Material: Stainless Steel + AluminiumColor: Shown As PicturesPress Tool Size: Approx. 12 * 10 * 20cm / 4.72 * 3.94 * 7.87inchRound Size: 18/20 21/23 24/26 28/30 31/32 33/34 36/38 40/42 43/45 48/502 Round Dies: 16/16 20/25mmSquare Size: 20 25 30 35 40 45mmShield Size: 37 45mmWeight: 1620gType: Repair Tools & KitsPackage List:1 * Watch Press Tool20 * DiesNote:The measurement error is about 2 mm, thank you for your understanding.There is an error in the size of manual measurement, thank you for your understanding.Instructions:1. Choose a die which is bigger than the watch crystal and install it at screw-socket of under pliers.2. Choose other die which is smaller than the rear cover and install it at screw-socket of up pliers.3. Put a watch crystal adown at the under die and put the rear cover at a suitable position.4. Lightly press down.5. Putting a cloth under the watch crystal will protect the watch crystal.