DC connectors are also known as coaxial power connectors are sized based on their outer and inner diameters, for instance, sizes such as 6x4mm, 5.5×2.5mm and 4×1.7mm. DC connector are designed so that the larger number is the outer diameter, this would be the outer diameter of the male part or the size of the hole on a female part. While the smaller number relates to the inner diameter, this being the hole on the male part and the diameter of the inner pin on a female connector.