A medical device shaft including an unbalanced braid reinforcement layer. The reinforcement layer may be an unbalanced braid by having a first set of strands and a second set of strands, the sets wound in opposing directions on a mandrel or on the device shaft. The first set and second set may have different numbers of strands, sizes of strands, or pitch, or combinations thereof. In some embodiments, the unbalanced braid increases contact area between the inner layer and the outer layer of the shaft without compromising the function of the braid. In other embodiments, the variations in strand size and number between the first set and the second set allows improved kink and torque performance in a reduced thickness braid layer. The improved shaft of the present invention may be incorporated into a wide variety of medical devices such as guide catheters, diagnostic catheters, balloon catheters, etc.
