These are for use with this cable chain http://www.thingiverse.com/thing:34661
I used 20 links, plus these 2 ends.
Attached to the bed with an M3 screw and a tiny washer.
Attached to the frame with an M4 and a T-Nut (an extra that came with the kit)
Folger Tech RepRap 2020 Prusa i3