I made an external filament guide to add to the top of a Greg's or other extruder for better guiding of the filament. I found that mine usually misses the guidler one and so I added this to the other side on top of the extruder housing. I like my Guidler to be back a little so the bolts will not pop off, so I needed this for a little extra help.Print and secure on top of the extruder where the pocketed nuts are. I was not too worried about needing to replace the nuts anytime soon, so I just used a little acetone for glue and bonded it directly there. I used .33 layer ABS, nothing special. Only had to shve the notch a hair to get a nice sliding fit.