Soda Stream Crystal - bottle cap marker

We use several Soda Stream Crystal bottles at home, usually everyone has his own bottle. The problem is that they all look alike. And because there are no coloured bottle caps I made this snap-on marker, so that everyone can mark ones own bottle.

___History___
v2: I made the marker a lot smaller because the original design was harder to use (it turned when you didn't grab it right). But the original design is the one I like more sou you can choose by yourself which to use.

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