I just got these Trail Gear chromoly spindle nuts, but have not installed yet.
Observation: There are manufacturing quality deficits in the finishing, done too quickly, but the basic machining is OK.
Some hand re-work was required to get the lock-ring through holes to line up with the lock-nut threaded holes.
- As received, the M3.0x0.5x10 retainer screws would not thread into the lock-nut, as if the holes were misaligned.
I almost sent them back as defective...
Recommended hand re-work :
1) Run a tap through the threaded lock-nut holes to clean up the final finish chamfer burrs.
Then everything lines up OK. Everyone has an M3x0.5 tap laying around, right?

2) Clean up the burrs on the main lock-nut spindle thread chamfer.
Some delicate work with a Dremel fine sanding drum, maybe a little hand sanding.
3) Flat sand / planerize all the flat mating surfaces a bit - a sheet of 600 grit wet-or-dry on a flat surface.
4) Clean up the lock-ring tab edges where there is some laser cut swarf - fine details.
I found the M3.0x0.5x10 button head cap screws at my local Ace Hardware - Buy 10 and keep handy.
I'm pretty convinced this is an improvement over the stock double lock-nut arrangement.
It provides a more stable support to apply pressure to the roller bearing race, will yield less under load.
The stock stock double lock-nuts are each half as thick, and they are tightened against each other, so, only one of them is applying preload pressure to the race. The threads have tolerance slop, are made out of soft steel, and are only about 2-3 threads deep. So, there isn't much averaging going on to even out variations in exact thread engagement. Under the leverage of a big tire, how much will these 2-3 threads deform? Some.
The Trail Gear nut is twice as thick and all the threads are load bearing against the race - more evening out of tolerances, and a stronger material too.