The Concentration Ring (霊撃輪具, Reigeki Ringu, literally translated as Spirit Strike Ring Tool) is the third of seven devices from Yusuke's Spirit Detective kit.
The Concentration Ring is a gold ring with seven spokes pointing outward from the broader end. Its body possesses a small stud in-between a pair of spokes, for a total of seven.
This device multiplies the available Spirit Energy of its wearer several-fold. Botan mentions that, once he uses this device, Yusuke will be severely-exhausted afterwards.
After Yusuke's first unsuccessful fight with Gouki, Botan gives this device to him, saying that she had initially intended to save this device for when Yusuke's Spirit Energy reserves had grown.
Apparently, it would enhance the punch of his Spirit Gun, but leave him completely exhausted afterwards, so she warns him to use it as a last resort.
He uses it against Gouki later on with great success.<ref name="Episode_7">