Rolling Thunder Game Calls PureDuck Duck Call PureDuck Duck CallSince 2001, Keith Allen has been building duck calls with one singular focus: delivering a 100% pure duck sound. The PureDuck is the most versatile, user-friendly J-frame call in our line, and it's the perfect lanyard-mate to the loud cutdowns that Rolling Thunder is known for. It features a traditional 1/4" initial bore that opens up to a medium size bore.The PureDuck provides clean tones with plenty of range and easy transitions, from high-end hails to bottom-end feed calls.