Most of unmanned builders always need to measure if this and that are in level. Well that sparked an idea. Why not to look small water level gauges for swag shop. First batch is about to come. Here is some pre-shots 
They are 16mm in diameter and 6mm high…
Text is laser engraved on top of the lens. It be colored too to enhance the text. Or in future we can have silk print on them too.
Ideas, comments welcome
These small ones are only good for approximation of level. I recommend to go with something bigger like this https://www.banggood.com/60mm-Large-Spirit-Bubble-Level-Degree-Mark-Surface-Circular-Measuring-Bulls-Eyes-p-1141357.html?rmmds=search&cur_warehouse=CN It’s still dirt cheap.
Andras, yes those bigger ones are good too and most likely will be added to shop later on. Dirt cheap or not, that is not real value as they need to be branded as ArduPilot texts and then add small margin that ArduPilot group will get.
Yepp, I mean by “dirt cheap” that their price will be reasonable even after branding and adding margin 