5/8/2015 D nock Series 2 (i.e. D2) Due to the fact that PSE has made the factory nock on TAC bolts non removable starting in August 2014, many customers have chosen the Firenock AeroBolt II-200 26" instead of the TAC bolt. The original TAC bolt has 0.298" ID while AeroBolt has 0.300" ID. As we originally designed the D nock to fit 0.298" ID perfectly, the D nock could be a bit loose on the Aerobolt. Also many customers have discovered the high reliability of the D nock and used it on other 0.300" ID crossbow bolts. Due to the demand, we decided to make another D nock to fit 0.300" ID perfectly. Thus D nock Series 2 (i.e. D2) was introduced. For those who use 0.298 ID arrows (e.g. original TAC bolts, Easton arrows), please use the D1. For those who use 0.300" ID arrows (e.g. Aerobolt, Black Eagle Executioner, Gold Tip Laser III, III), please use the D2.