The Proof of Life Flies combine just the right amount of realism with durability and heavy weight. Put plainly, they are serious nymphs for serious nymphers. The POL Golden Stone is a must have for big water trout, like the Lehigh and Upper Delaware Rivers, and have absolutely laid waste to steelhead in the right water conditions. Trout love stonefly nymphs, even in many streams and rivers without significant stonefly populations, and these nymphs are just the ticket.