I have no doubt that the RnB pack is well designed and fits the stock Equinox very well. But for the benefit of folks that use an aftermarket arm cuff, it may be worth taking a careful look at the dimensions, exactly how the pack attaches and lays under the shaft, and how much clearance your cuff affords the pack.
In my case, I use Herke cuffs as a replacement for the plastic stock cuff. The cuff has a triangular shaped detector stand, and the apex of the triangle where it meets the shaft would likely interfere with the pack’s alignment and/or attachment (see pics below showing the Herke cuff vs stock). Just something to consider for aftermarket cuff users.
All that said, I’m with Toy Soldier…besides my concerns about the fit with the aftermarket cuff, the other reason why I decided against trying the power pack is that I felt it was unnecessary for me. On the rare occasions that I do an all day hunt, the on-board battery still has plenty of juice left starting from full. I was at a weekend event last March, and detected from dawn to dusk both days…my 2 1/2-year-old equinox battery lasted the full day with no problem, I just topped off overnight between the two hunts at the hotel. I do have beefy 26800mAh power packs that I keep in my backpack to charge devices if necessary, but so far I’ve only used them with earbuds and my cellphone - never needed it for the detector. At 3 1/2 years old now, I haven’t noticed any major battery degradation…it easily handles my usual 2-5 hour hunts.
Luckily I only have 2 detectors. Even those are interchangeable.
and I should have it next week sometime. 
