This is what a Brass Catcher should do:
1. Catch the brass, so you don’t get hit by it, so it doesn’t hit other shooters, and so you don’t have to pick it up or hunt in the grass for it.
2. It should not fall off during normal operation of the weapon. I don’t like the velcro attachment techniques since they never seem to hold securely. Attaching to the unused parts of the rail works nicely. I wonder why the AR accessory guys don’t make those that way.
3. If you want to take it off, it should come off easily.
4. It should not interfere with the normal operation of the weapon or any of its features.
5. It should be constructed of a soft material that won’t catch fire, melt from hot brass or be so brittle that it fractures from brass impacting it.
But I have just learned that they make Kydex in clear. That allows you to check the chamber without removing the catcher and easily see if it is jammed.
I can see there might be a V 2.0 in the near future.