These kind of jumpers lay flat on the breadboard and seat far more solidly than the floppy jumpers you mostly see.
They are made of stiff wire-wrap wire with the ends stripped and bent down at 90 deg. They can be a PITA to insert after the first use if not on first use. I use needle nose pliers (thin ones for fine work) to straighten bent ends and to push them in the hole.
If the holes are not exactly the length of the jumper, bend it to the side to lay flat on the board. That bend helps the ends hold harder.
These jumpers don't slip out of the holes. In fact, removing them takes effort and is more of a PITA than inserting them.