I bought several 2 1/4 and 2 1/2 grade eight bolts from our local comercial hardware store. I'm using a ATI dampener with a extend hub to use with a milidon gar drive, the stock BB bolt woulndn't engage one thread I had one stock SB bolt and I used it to seat the dampeener and it was way long on the thrread engagement so I bought the others one for future use, I ended up using one of the 2 1/4 long ones