One side is rounded and opposite open end is square.  As such, this is impossible to crimp with round shape.  I used round cutters of wire stripper to install these on round shoe laces about 1/8" thick.  Per one review, I used superglue gel.  Glue will leak out the holes so be prepared to get some glue on the fingers.  Without some kind of special tool, this is about the best option for repairing the usual plastic aglets these days.