All cats require the ability to get their claws over-the-top of any fence, when you install a 2" pipe at the top of your fence, they never even attempt to leap over your fence. I know because after 65 days of installing the system around 193ft of my backyard fence, not only did my fence leaping cats never attempt to jump the fence but we have "caught" 2 outdoor neighbor cats that jumped into our backyard over night and could not get out until we opened our side gate in the morning. 2" ABS black plumbing pipe (this is UV rated) and 2" rigid straps placed 2 per pipe section.