the sks fender in that photo is waaaay to high. in order to be effective, it needs to be about a centimeter and a half above your rear wheel, assuming it's a hardtail. i don't use that brand, but mine is stiff enough that it doesn't flop down and hit the tire. if you can't get it low enough on your seatpost, try mounting it on the seat tube, so that it sticks out through the chainstays just above the brake bridge.