They’re all different sizes. It’s not just the diameter, but also the thread and length. I have two Trek road bikes and they have different rear axles for example. There’s not even a coding system. It’s a big mess.
The best deal out there are J&L on ebay. They’re either the lightest or very near it as well as the cheapest. If you need something they don’t have listed, they’ll make it. I’ve got 4 of these