Incredible that you can get an axle to your doorstep for what plumbing pipe would cost at Home Depot.
Regarding plate compatibility - it's a little hit-or-miss. High end ones won't fit as is, but most you'd see at a crossfit gym would be fine. Here's what I had at the gym to test with - we mostly use the Echo Bumpers for strongman stuff:
Rogue Echo Bumpers - fit but snug
Rogue Training 2.0 Plates (Competition style bumpers) - doesn't fit
Pendlay Competition Bumpers - doesn't fit
Rogue Calibrated Metal Plates - doesn't fit
York Legacy Milled Iron Plates - fit fine
Troy Interlocking Plates - most fit, some didn't
So the proper outside diameter of a bar is 50mm, which is a little less than 2". In the US, most axles are made with plumbing pipe, which is 1.5" inside diameter and like 1.87" outside diameter. That means plates are loose and regular collars don't work. If you used 2" outside diameter steel tubing or rod, only the cheapest metal plates fit, because cheap plates tend to have extra big holes due to lower tolerances. Now in China or wherever this is made, they use metric sizes for steel, so this appears to be 50mm outside diameter tubing. So that should be perfect, but it might not have very tight tolerances (the outside diameter might vary a bit), and they powder coat on top of it which adds some thickness. I'm pretty sure after sanding the powder coat off with a flap disk the high end plates would fit but I haven't tested it yet. And the Rogue Echo plates that were kind of tight when I got it are sliding on a lot better now after a few months of use.
As an additional side note, mine weighed like 26 lbs, not quite the 30 advertised.
On Titan equipment in general, the welds and powder coat job aren't perfect, but pretty good.
But, it's so so cheap, and shows up at your door in 2-3 days. You can buy 3 of them for less money than a Rogue one with shipping. If you're concerned your plates won't fit, you can buy this axle, an angle grinder, and flap discs, and you'd still be paying only a little over half what you would buying from elsewhere.
If you want a high-end axle though, I'd still get an Ironmind - one of the only ones with the proper diameter for regular collars and built stronger than the plumbing pipe axles. But Titan is second to none for a decent axle at a ridiculously low price. I'm giving it 5 stars despite some flaws because the price is so good it's still a steal.