Dankung unified tester of band's power

There was no an economic universal method to test and record how powerful a slingshot band is.
Chronograph is a good tool to test band's power, but it's expensive and too bulk size to easily carry.
Here in China, now this thick red bu*l can is used as an unified tester of bands' power. It's cheap and easy to carry.
Not all red bu*l works, as they are made with diffrent materials. This red bu*l has been used by majority shooters as it's sturdy and thick. Samples are,
"my 4-strand 1745 bands can hit trough Dankung red bu*l can from 3 meters"
"my SHESHOU band can hit through Dankung red bu*l can from 15 meters"
With this unified can, the power of band can be easily tested and communicated among shooters.