Ken Morrish's Thunder Egg series was originally tied to catch steelhead in the Rogue River basin in southern Oregon. Thunder Eggs are constructed around heavy lead-eyes, and are designed to be fished in tandem with other unweighted egg patterns. They act as sinkers in fly fishing-only rivers where external weight is banned. You will be surprised to find how many trout and steelhead actually pass up your more realistic offering to grab the Thunder Egg.
The bright pink version is an even more garish version of the Thunder Egg. No fish in our rivers spawn eggs that look anything like this bright fluorescent pink ball of sparkle chenille, but fish often eat them anyway. And to make things even more perplexing, these bright flies seem to attract more fish than realistic egg patterns. It is one of those mysteries - like seeing trout trying to eat your brightly-colored strike indicator.