87mm Quad.  Req'd parts:

• PikoBLX Flight Controller (or anything else with a 20x20mm hole spacing)
• ESCs smaller than 23x14x5mm or so - I recomment the Racerstar RS6a 2-3s, but in theory anything as big as a Littlebee should fit.
• 1104/6500 are known good, I expect 1103/8000 would be fine as well on 2s for something a little less high strung.
• I'm using the InnovaOSD/VTX from Furious, but there are options for VTX - note that at this size you don't want a full flavor SMA connector on the frame anywhere.  Nowhere to put it, anyway.
• The 12x12mm diatone cam and mount works nicely, but this is the most DIY part of this build.  If you don't have a 3d printer, I recommend the Diatone variant of the top, it just bolts up, no muss, no fuss.
• The smallest radio receiver you can find.

Assembly is pretty straightforward, although tricky.