Bone Collector The Contender Deer Grunt Tube Call - If you are seeking an easy-to-use grunt call that produces most deer vocalizations, then look no further than the Bone Collector Game Calls The Contender. By changing the placement of an o-ring, The Contender can morph from a doe-in-estrous to a young buck to a mature ol' mossy horn grunting. One call, all the sounds...what more do you need. How to use Select vocalizations by moving the O-Ring up or down the reed channel. All the way down for adult buck, all the way up for a fawn bleat. Blow air in to the reed end of the call. Adjust the amount of air to adjust volume. Hands can also be used to change sound and volume by cupping the end of the barrel.