We get cores from several different vendors. Most of our roller cores come from Callies. The Callie cores, so far, have the highest c-scale rockwell at 62 and I prefer that core. We have 3-piece cores from Camshaft Machine for a lot of the street cars that don't want to run a bronze gear. We also get cores from Engine Power, mainly for our cast and SADI stuff. We do have some Callies 3-piece cores. We trying to expand our inventory in the Callies 3-piece cores, as those have the same 62 c-scale rockwell hardness. Working on a few more videos that will be a little bit shorter and hopefully informational for everybody.. Thanks for checking us out.