I ride a Catrike Expedition. On the flag staff, on the lower portion that came with the trike, I drilled a hole through a wine cork and mounted it on the upper portion of the lower pole, with a set screw so it could not turn, and to this I attached a Planet Bike strobe "blinky" red facing aft. I drilled a small hole through the trike fitting that holds the pole on the frame of the trike, and through this, I inserted a "hairpin" that prevents the flag pole from twisting. This makes it easy to take the whole thing off of the trike when it's on the bike rack behind the car. The light flashes at about 5 feet above ground; very visible. It's been a great system for years and I'm told I am visible to anyone coming up from behind. The flag I use is from "Be Seen Wear". Mike