The ones I have are called "Cast Connectors" They come in Fl Orange and clear.
Here's how they work. They are barrel shaped with an axial hole and a 180
degree radial hole at the mid point. Put the line in an axial hole and out the
radial hole. Tie a knot, trm, and put knot back into the barrel. Put the
thick part of the leader in the other axial hole and out the radial hole . Tie
a knot trim, and put the knot back in the barrel.. Also; they make it easier
to land fish (on the rare occasion I catch one). They slide through the guides
smoothly. I used to reel in to a point where my line was still extending out
the tip top. Now I reel into the point where the leader length extending out
from the tip top is the optimum for using the net.