Maybe you got outbid on yesterday’s DEVO art bike and you’d like to use your current bike to make your own art. For that you need the Contrail, a tool that attaches to your bike’s seat tube and leaves a colorful chalk line behind you as you ride. Brooklyn’s Studio Gelardi says they created it to build biker community. The Contrail holds 200 grams of chalk — enough for about 20 miles of riding — all the while leaving a faint line that reminds fellow cyclists where it’s safe to ride. As bikers follow, the chalk lines grow brighter “reclaiming the crucial shared space.” The Contrail was a finalist in Design 21’s Pedal To The Medal competition and is not in yet in production.