This is what we use for splicing monofilament inside of dacron or our Diamond Braid hollow core line for top shots or wind-on leaders.
The splicing kit comes with 5 threading needles, a loop splicing needle and a reverse latch needle that will make splicing 80lb through 200lb test mono easy. Individual needles are available to handle monofilament lines up to 500lb. Just insert your monofilament into the end of the needle. Heat the mono line at the tip and insert it into the end of the proper needle. Using the proper tools makes for strong clean connections when making wind on leaders or just plain splicing hollow core lines.