YJYOYO - Bi-Metal Rim Alignment Tool.
Outer rim bi-metal yoyos offer some of the best possible weight distribution you can get in a yoyo, but they are also easier to damage or dislodge when hitting the ground. The YJYOYO Alignment Tool is a specially designed tool that allows players using external rim bi-metals to straighten the rim directly.
If you notice your rim is no longer sitting flush with the yoyo body you can simply unscrew it, lay the yoyo on a durable flat surface (rim down), place the Alignment Tool opening over the bearing area of the yoyo and tap it a few times with a rubber mallet or hammer. The rim should reseat itself in the proper position and you can get back to throwing!