These parts go on the middle 4 pillars of the ZMR250 quadcopter frame.
When assembled, they create a protective cage around the battery to stop it from being damaged during a crash.
If used with padding, it will stop the battery from rattling around, keep its self closed and be easy to open when needing to access the battery.
This is designed to fit the Turnigy Nanotech 1300mAh 3S LiPo battery, but it may fit others of similar size.
Printed on an Ultimaker Original
More details about the design on my blog post: