Carbon Tech's McKinney Nock system is designed for accuracy.  The durable and accurate polycarbonate nock is developed to fit Carbon Tech's own Nock Adapter System which includes our CT Cheetah, CT Whitetail, CT Rhino, CT Panther.  Also, the CT Hippo and CT Orca.  Easy to tune.  One size fits all, including the X10 and ACE systems! 4.2 grains. Comes in a pack of 1 dozen.