If you use the plastic bags in the snow, you can't have much snow over them, especially if it is wet packy snow, the bag will push all the snow up and the critters foot out of the trap. Some of the guys up north swear by them and claim the cheap plastic bags shatter in the cold. It isn't usually that cold here and I had nothing but misses with them. I went back to wax paper. I've used coffee filters, they work but tend to deteriorate in the wet and sometimes cause a slump and expose the pan if it was dry when you set it and there is any air under it.