Poor quality control.

I have a half dozen Thunderglo Lighted Nocks from NAP Archery, but only two of the six nocks light up and are functional. The quality control is poor, as each piece varies in size enough to make a difference in how each fits. Also, some nock lights press and light up with ease, but others almost need a mallet to depress the nock to lit position. Once again, of the six, only two actually light up.