If you mean fishing line, the strongest matches in this set are leader and main-line options.
Seaguar Threadlock® is the main-line choice when you want thin diameter, no stretch, and easy knotless leader connections for heavy-duty or offshore setups.
Use fluorocarbon leaders when fish are line-shy, when fishing around rocks, docks, or other cover, or when you want a lower-visibility connection ahead of a lure or hook.
Use Seaguar Threadlock® as your main line when you need maximum sensitivity and direct hooksets, then add a leader if needed.