The red is bright enough that cars actually notice it hanging off the back of my kayak. Attaching it took about a minute and it stayed put the whole drive to the lake.
Miles★★★★★
Bought this because my state requires a red flag on anything sticking past the bumper, and it clips onto the kayak stern in seconds. Stayed visible the whole drive home on the highway.
Victoria U.★★★☆☆
Does the job of keeping me legal, and clipping it to the kayak stern only takes a second. The flag itself is pretty thin, though, and it flapped itself into a wrinkled mess after a couple of highway trips.