Another of Red Witch's diminutive Seven Sisters stompbox range, the Ruby offers a functional two-knob fuzz, and 300 hours of use from a single charge of it's lithium battery, alternatively/in addition you can use a 9v adaptor.
Volume and fuzz knobs dial in the sound, which is voiced somewhat like sister model the Fuzz God II with its sputter knob fixed at around 2 o'clock. Ruby's not a polite lady; what she gives you is raucous, spitty fuzz with an attitude. We like it.
So what of the battery? Well, considering that most of us run our pedals off a power supply rather than batteries these days, and you do need an adaptor to charge it anyway, perhaps it's not that relevant.
It will impact in two ways, though: one (good) is that it will still work if your power supply goes down onstage; and the other (er, not so good) being that lithium batteries need replacing every couple of years.
Characterful fuzz with plenty of appeal, although a little more output would have been nice, rather than having to keep the volume knob almost fully up.