It's 3M Scotchlite tape, an inch wide and twenty-seven inches long. It's silver, and you put it anywhere you like, and it screams bloody murder when headlights hit it at night, and even when the sun hits it at the right angle during the day. Put it on your bike and you'll never be truly invisible at night, even if you're lightless.
Fenders are an obvious spot, but cranks are especially good, because the movement helps. Click through the pictures and you'll get the idea. The wheel reflectors (also visible in some of the pictures) are a separate item--although you could conceivably do that with this tape, too. But it won't last well unless it's on a solid background, so just put the tape on solid things. One or more of these photos also shows the our ankle reflector . The tape is on the cranks. It's good there, because you don't take it on and off. I round the corners before I put it on, because corners tend to lift off. I urge you to become, as I have become, a member of the "rounded tape corners" club.

The main picture shows the reflectors on our Sneaker Pedals and this tape on the backside of the crankarm.
Some of the other photos show the tape on the cranks, too. They show other reflectors as well, but the cranks is what you want to look at.

But of all the reflectors we sell, have seen, or are out there in this vast stone most free-to-roam&generally employable people call the world, the brightest is this 3M Scotchlite tape. Every fender needs some, for sure; and put some on your crank arm while you're at it.