Passive USB extender cables do not meet the USB standards and thus are forbidden to carry the USB logo. The only cable structure recognized by the official USB standards is one with an A plug and a B plug (such as Micro USB, Lightning, and USB-C among others) at either end. This restriction was intended to prevent cable lengths greater than the maximum allowed by the USB standard from being assembled and to avoid an accumulation of resistance in the connections exceeding the design limits of USB, in order to ensure consistent plug-and-play operation of the USB system without the need for users to calculate cable lengths or enforce technical rules.