It is, but and free-ranging or cup escapee bugs, can and will chew through it and escape the cage into your home. Just use aluminum.
edit: Does LLL even sell screen? I just looked at their store categories and didn't see anything that would indicate that they did.. I dunno. Either way I wouldn't pay shipping on something that can be bought locally and is probably much cheaper. You can find rolls of aluminum screen (enough for one cage) at Home Depot and Lowes, for less than 15 bucks. I want to say less than 10 but am not 100% sure.