This is a housing for an optical filament run-out sensor. The center section allows for some adjustment for a sensor that comes poorly soldered thus in the wrong position like I ran into.You will need an M2 10mm bolt and nut to tighten the center adjustable piece and 2 small screws for the bottom cover. It is meant to mount in the Robo top slot. For info to incorporate this into a Robo 3D R1 see:
12/27/2016 Added version 2 (all files with V2 in name). Version 2 incorporates the through slot (remixed) that comes with the Robo R1 and the filament out sensor swivels on the top of that through slot. It uses PTFE meant for 1.75 mm filament for the guide holes. The top piece is optional but the bottom piece is pretty much required. The bottom piece of PTFE inserts from the inside of the adjuster piece and is only about 4.5mm long. Without it you will probably get false triggers since there wouldn't be much to center the filament in the optical sensor. The top piece of PTFE is about 35mm long but is optional, This version requires an M2 12mm machine screw and an M2 insert (there wasn't room for a nut) The insert is melted into the bottom of the adjuster so that it is adjustable via the machine screw from the top. I printed the lightGuide with t-Glase which makes a fairly good light guide.
Note: I have modified the top housing to allow for more room incase the sensor is off center or whatever. It was a little tight before.