SMRTFT NUOBELLs are designed to hold the round plates on the dumbbell in multiple ways. First, the handle extender extends through the middle of the plates. Second, the tongue-and-groove system at the top and bottom of each plate, where connectors interlock to secures the plates to one another. We recommend that you check that everything is set up properly prior to starting a workout with any equipment you use to get stronger.