This is a camera filter holder for nikon 77mm DSLR cameras/lenses. it is modular, so that you can build it to attach 1 or two or three filters in a series. to join brackets and frame, use a M3 screw. Lenght depends on how many layers you use. The brackets hold a filters of 130x170x4mm. frame and camera mount prints with no support, print brackets on their side (bendy bit up) with supports under the bendy bit. :-) 0.2 layer height, 20% infill, 3 perimeter layers.