Really Works!
We have a large house surrounded by trees.  Would be catching mice in the attic regularly.  And then we had an invasion of flying squirrels - cute little critters but they belong outside.  We used humane live traps to remove the squirrels as they showed up and released them in a field with a hollow tree 2 miles away.  Then added one of those sonic devices meant to drive rodents out.  Also tried flashing strobe lights (which helped a little).  We even had roofing installers who put on our new roof to do a complete inspection to find/fix possible entry points but the critters still found a way in.  Then I found these rodent repellant balls and wow!  Put one in each end of the attic and have not seen any activity since!  I put inexpensive IP cameras in the attic tied into my home security system to keep an eye on activity so I know that these balls are keeping rodents out.  It is a real relief to have finally found something that works.  I'll be keeping a supply on hand.  One caution -- the smell of these things is no-kidding strong.  Use gloves to handle and avoid contact with clothes.
Rating: 5 stars