You just have to Email Troy at www.b-p-p.com. He always shows the 1020/15 as out of stock, but he gets them in and sold so quick he never updates his website. He might have them, you just have to ask. I got the Cobri gearbox from www.e-flightline.com but B-P-P has them listed as in stock, just not yet on the site. The 1020/14 is always in stock, you could run one of them with the 12 tooth pinion (that's the smallest that will fit on the Lehner shaft) and like a 76 tooth spur, and have almost identical performance to the 1020/15 and a 12 tooth pinion/ 70 tooth spur.

I would not run anything but the Cobri gearbox on this motor...just not worth it.

4000X11.1=44000/5.83=7615 This is the 1020/15 at 4000Kv on 11.1V nominal and 12 tooth pinion/70 tooth spur (My Set Up)

4286X11.1=47575/6.33=7515 This is the 1020/14 at 4286Kv on 11.1V nominal and 12 tooth pinion/76 tooth spur (In Stock Set Up)

Of course the pack voltage drops when you hit the throttle, those numbers are just for comparison. That is the theoretical no-load RPM.

That's really close, actually a hair easier on the packs with the 1020/14 at 6.33:1

And as a side note... I turn the 12X6 APC SF prop at 86% of the above calculated RPM. Of course, the voltage is at about 10.1 when I tached it and all, so this is not a measure of system efficiency, just an interesting tidbit.

As another side note.. I took my measured RPM/Theoretical No-Load RPM at 10.1V and got 94% efficiency. And that is thru the gearbox.