A fastener comprising: a first end ; an oppositely disposed second end ; and an elongate portion intermediate the first end and the second end and defining a longitudinal axis of the fastener, wherein the elongate portion comprises: a generally cylindrical first region adjacent to the first end , extending a distance along the elongate portion , and having a first diameter (Φ 1 ); a generally cylindrical second region adjacent to the second end , extending a distance along the elongate portion , and having a second diameter (Φ 2 ) different from the first diameter (Φ 1 ), wherein the second Z diameter (Φ 2 ) is less than the first diameter (Φ 1 ); and a transition zone extending a distance along the elongate portion and connecting the first region and the second region , the transition zone comprising: a radiused region comprising a shoulder defining a radius of curvature in a range of 0.005 mm to 0.5 mm (0.0002 inch to 0.02 inch); and a taper region intermediate the first region and the radiused region and comprising an angled surface defining an angle in a range of 2 degrees to 10 degrees relative to the longitudinal axis preferably defining an angle in a range of 2 degrees to 7 degrees relative to the longitudinal axis . a first end ; an oppositely disposed second end ; and an elongate portion intermediate the first end and the second end and defining a longitudinal axis of the fastener, wherein the elongate portion comprises: a generally cylindrical first region adjacent to the first end , extending a distance along the elongate portion , and having a first diameter (Φ 1 ); a generally cylindrical second region adjacent to the second end , extending a distance along the elongate portion , and having a second diameter (Φ 2 ) different from the first diameter (Φ 1 ), wherein the second Z diameter (Φ 2 ) is less than the first diameter (Φ 1 ); and a transition zone extending a distance along the elongate portion and connecting the first region and the second region , the transition zone comprising: a radiused region comprising a shoulder defining a radius of curvature in a range of 0.005 mm to 0.5 mm (0.0002 inch to 0.02 inch); and a taper region intermediate the first region and the radiused region and comprising an angled surface defining an angle in a range of 2 degrees to 10 degrees relative to the longitudinal axis preferably defining an angle in a range of 2 degrees to 7 degrees relative to the longitudinal axis . a generally cylindrical first region adjacent to the first end , extending a distance along the elongate portion , and having a first diameter (Φ 1 ); a generally cylindrical second region adjacent to the second end , extending a distance along the elongate portion , and having a second diameter (Φ 2 ) different from the first diameter (Φ 1 ), wherein the second Z diameter (Φ 2 ) is less than the first diameter (Φ 1 ); and a transition zone extending a distance along the elongate portion and connecting the first region and the second region , the transition zone comprising: a radiused region comprising a shoulder defining a radius of curvature in a range of 0.005 mm to 0.5 mm (0.0002 inch to 0.02 inch); and a taper region intermediate the first region and the radiused region and comprising an angled surface defining an angle in a range of 2 degrees to 10 degrees relative to the longitudinal axis preferably defining an angle in a range of 2 degrees to 7 degrees relative to the longitudinal axis . a radiused region comprising a shoulder defining a radius of curvature in a range of 0.005 mm to 0.5 mm (0.0002 inch to 0.02 inch); and a taper region intermediate the first region and the radiused region and comprising an angled surface defining an angle in a range of 2 degrees to 10 degrees relative to the longitudinal axis preferably defining an angle in a range of 2 degrees to 7 degrees relative to the longitudinal axis . <EOS>