Great info:
Catch Cans
But it says:
Not all Catch Cans are created equally! Most Catch Cans on the market are just comprised of an empty container with 2 ports. While that simple design may trap a few oil droplets, our Catch Can is designed to condense the oil vapor and trap the oil inside the container.
Our test proven design incorporates a stainless steel mesh and screening mechanism that acts like a maze to collect and condense the oil vapor.
I have seen a lot of people adding steel wool for that reason anyways...