I have Da Brim mounted on my helmet and it's a permanent part of my riding kit. I like it because it shades your face, your ears, your neck and your eyes, whereas a ball cap or riding cap only shades your face and eyes.

They make 2 models and I've had both. The "big" one was prone to flapping in cross winds when traveling fast. I then got their smaller version and it's a winner. It is permanently on my helmet.