I have one of these and it works surprisingly well. The gray squeegee looking flap flips back and forth as you roll it causing the red strips to take turns sliding into the cylindrical housing where they get wiped off so the hair collects inside. It essentially relies on the red strips short fibers snagging hair better than the fabric you’re wiping it on which is usually smoother (the only thing I could see it not working on would be like a really fuzzy soft sweater or something with its own stiff short fibers that catches hair). Static might be helping there too.