I've had a couple of requests for this. I had one made a while back but couldn't figure out the single point sling mount until recently when I got the time to work on it. The endcap file has no holes, the one with I at the end has one hole for a eye bolt. The one with U at the end of the file name has two holes that work with a u-bolt. The eye bolt I used was 1/4" x 2" eye bolt, I had to cut the threads at the end off due to it being too long. The u-bolt was a1/4" x 3/4" x 2 1/2" and cut the threaded ends down with a grinder to fit. The print settings are 0.3 mm layer height, 10% infill, 2 shells, no supports and was printed using ABS filament.