This is 2 parts to make printing easier. I make a lot of GoPro mounts but I was never 100% happy with them, too tight, too loose, holes too small.... So I completely redesigned this one and I may be updating my other models with this connector. Also, I found something important for printing thin walled items like the GoPro mounts (fingers), it's important to only have 2 perimeters and then 100% infill. I use to print with 4 perimeters but it turns out that is way too weak because of layer adhesion. See this thread for the full story http://forums.reprap.org/read.php?262,357700