In this version, a finger ring is borrowed or brought into play, which links to a ring. A lot of creativity went into this effect, but I don't find the effect to be all that useful when added to a great close-up linking ring routine.
Familiar Ring
For "Ninja +," Matthew Garrett has created a wealth of moves that range from standard crash links and various un-links, as well as switches, and cool variations that involve two rings and a single ring in different configurations. I do like the idea of linking a ring onto a finger ring, which I think can be a routine in itself. This can also work nicely as a follow-up to a finger ring on string routine.
The combination of the moves and gimmicks is quite convincing. Garrett also teaches lots of flourishes with finger rings and coin moves that he has adapted, and there's even a move with rope. Throughout, he offers excellent instruction.
Downsides?
Rings and Fine Array
The linking ring, while nice, doesn't match the quality of a standard Ninja ring - I can see the weld mark and I think spectators will find it as well. Another difference, albeit, a minor one, the Ninja+ rings are slightly thinner than standard Ninja rings. Spectators won’t notice, but I could tell that the Ninja+ rings were lighter.
So is this a "must have" if you already perform a commercial and entertaining close-up linking ring routine? My take is "no." But if you like the idea, Matthew Garrett provides the moves and props that will allow you to effectively do this.

