Step 1: Examine your case, 2 buttons or 3 buttons? Step 2: IMPORTANT STEP Choose the model that suits you. Be sure to check the size of the opening on your current case that allows the blade to enter so that compatibility is perfect. So 9mm/3mm or 9.5mm/2.5mm? Step 3: Order the model that suits you, once received, nothing could be simpler! Remove the battery, the electronic circuit and the blade from your old case and place them in the same way on your new case and you're done! Ideal product to replace a broken/worn case, or one with damaged buttons. Electronic circuit and battery not included (they are to be recovered from your old case) Note: The data are all measured manually, please allow an error of 1 to 3 cm due to differences in light and display, there may be color differences, please refer to the actual item received.