The Carbon Express Universal String-Loop Nocking Plier opens nock sets without damage, two hole size for nock set installation, pre-stretches D-loop, permanently tightens D-loop to string, heavy duty comfortable extra large grip.FeaturesPre-stretches D-loopPermanently tightens D-loop to stringOpens nock set without damageTwo hole sizes for nock set installationHeavy-duty comfortable extra-large grip