I really like rolling joints, but I much prefer using a bong. So I made a little adapter that allows you to stick your joint into the hole (I use filter tips and that's about the size they end up being). Fits a 14mm downstem and features a little funnel that works decently as an ash catcher. Fits http://www.thingiverse.com/thing:734700 pretty dang well (seen in photo). Careful with this - it hits like a freakn' truck.Printed at .38mm layer height, 20% infill, with supports and a brim, on EasyPLA. OpenSCAD source included in case you want to adjust.