Summary

Thanks to original source maker. This just adds a retaining string and clip to easily clip on and prevent cap being lost in the grass (yes we've all done that haven't we?).

Must be in a flexible and durable filament. I use TPU. And print 22 at a time then give them to grateful fellow RC club members. Easy and quick to print.

I use different colours to denote 3s 4s and 6s lipos. This helps prevent accidental catastrophies when parallel charging multiple packs simultaneously!