Adapter to add even more rails to your Nerf blaster. Refer to the picture for print orientation. You'll need (2) 8-32x1.25" screws and (2) nuts for this: https://www.mcmaster.com/#91251a201
https://www.mcmaster.com/#92362A130
The 'springs' snap into place over the main parts. The pointed end of the springs face the back of the adapter.
The STL file units are in inches - use math or google for the scale factor to mm.
I also sell this on Etsy: https://www.etsy.com/listing/594842061/nerf-tri-rail-adapter
Enjoy.