I can tell you about the weight, which you'll sometimes see as just Z. So, 4Z, 6Z, 8Z 10Z, 12Z. These essentially are the grade of the net material. The heavier the net, the thicker the material is (more strands in the line of thread that was used to make the net). Some people don't see this as being important, and sometimes they're right, but personally, I prefer a heavier net because I often set thick briar and brambles, hedgerows, forests, etc. A lower weight net tangles a lot better, so can have benefits when trying to tangle a rabbit, but not when you want to set in an environment like th