1.  Can I use 3rd party batteries with Battery Mag?  
Yes!  However, the Battery Mags have been specifically designed from the dimensions of the original manufacturer's batteries.  All 3rd party batteries I have tested (many, many, many) are either slightly smaller or slightly bigger than the original camera manufacturers.  So you may experience slightly looser or slightly tighter fits with 3rd party batteries.
2.  Can I leave the Battery Mag on my dashboard on a hot sunny day?
Not recommended.  Battery Mags are printed from PLA+ flilament, which is pretty tough, but not indestructible.  If you keep the Battery Mags in your camera bag, you are gonna be just fine.
3.  Are you going to make models for Fuji and Nikon?
Yes! Available Now!
4.  Are these going to be available forever?
I don't think so.  I'm a full time documentary cinematographer.  I've been doing that for 20 years now.  This is a side mission I've been wanting to do for a long time.  The travel restrictions from Covid-19 gave me a break from my regular schedule and I dove into this to fill the time.  So I suspect that when the travel restrictions are eased, I'll be back to shooting and won't have time to do this.
5.  There's little cobweb looking things on the surface of my Battery Mag, and the surface itself isn't smooth!
 The non smooth surface and occasional stringing (stringing is a term in the 3d printing world where thin strings about the size of spider web filament are sometimes created at the nozzle) is inherent in the 3d printing process.  We do our best to remove stringing artifacts, but they are inevitable.  The layered surface that comes with 3d printing is actually useful in this product, it acts as a bit of grip to keep the batteries in place, and it also creates a satisfying "zip" sound when you insert and retrieve batteries from the Mag.  
6.  When will I receive my Battery Mag(s)
We are caught up on all the backlog, most orders ship within 1-2 days!