Rollbe is here for all those times you've gotten into it with your friend Cornelius about how high or long or...girthy something is. The discs on these tiny wheels are either 4" (10 cm) or 8" (20 cm) around, marked in 1/16" (1mm) increments, so you can measure anything, anywhere, real quick and real easy. No lasers, magnets, apps, or making Cornelius hold the other end in place required.
Check out the GIF to see how the Rollbe rolls.
Karlis Krisjans designed the Rollbe to measure both straight lines and curved surfaces. Place either disc with its arrowed mark at your desired start point, grip its brass handle, and roll to your finish. You'll need a little focus and, yes, there will be math here too. To calculate the measurement, count the number of times Rollbe passes its arrow (you can also use its larger printed radius measurement as your visual cue) and then add the leftover inches / centimeters from the final, partial rotation.
For example, if you're using a 4" Rollbe to measure a package you're shipping and it makes 2 full rotations, and then stops on the 2-1/2" mark, the total length of that side is 10-1/2".
Rollbe can also measure inside corners - this is the second function of the ruler's radius indicator. Abut the disc against the corner, complete your roll, and then add the radius measurement to your final number.
The pocket-sized Rollbe is made of stainless steel and comes with a black or brown keychain pouch in case you want it to mind your keys as well. Measurements are laser engraved, and the edges of the discs are knurled to make the slip-resistant during use.
The Rollbe measuring wheel seeks crowdfunding on Kickstarter through August 30, 2017.