These high performance bearings are made in the USA for Hamilton Cams. For use when replacing the OEM bearings. 12 valve engines have one bearing on the first journal. Some Common rail engines have one on the first journal and one on the seventh journal. If you are using springs that have over 450lbs of nose pressure,or a steel cam, it is a good idea to machine your block to run bearings on all seven journals. Use HC-1 on stock size cam journals (2.124") Use HC-2 on our large journal cam Vincent (2.165") Both the HC-1 and HC-2 use 2.333" (+/-.0005") cam bore