The MK Unique Designs Grunt call kit. This call Kit is very versatile . 5 different Deer vocalizations can be produced by moving o ring to any one of 5 different settings on the. Sound board The kit also includes a extendable flex tube. This kit requires drilling 5/8 hole and13/16 and use stock at least 3-1/2" long. all you need is a barrel and lanyard.