Ray... Those pics in the charts are kinda generic. I personally have never seen a clutch head as pictured in the upper chart. Unless that is the largest size. The pic of #20 in the lower chart, are the same screws used on the Holley carbs. Those are the ones that I recognize as clutch. I remember seeing the drivers that we sold. The smaller size had more of a narrow waist. Where the larger size drivers had a wider waist.