This is a pack of six Tekno RC 6x17mm Differential Shims. These are the most current shims for the EB/NB/ET/NT48 and SCT410 vehicles. These are the hardest, flattest shims Tekno has ever offered. They are precisely manufactured for flawless differential action. It is unlikely you will ever need to replace these shims. While these are considered replacement parts, if you have an older gen Tekno vehicle, these shims are a must have update part.