There are two versions of this port. Most laptop computers do not have +12V power available, and have an eSATAp port which provides only +5 V. Desktop computers, with +12V available, have a port with two additional pads, placed against the plug's horns, which provide +12 V. Some manufacturers refer to these ports as eSATApd, where d stands for dual voltage. Some devices, such as 2.5-inch drives, can operate off the +5V supplied by laptop eSATAp ports. Others, such as 3.5-inch drives, also require +12V; they can be powered from a desktop eSATAp port, but require an external +12V power supply if used with a laptop computer. This can lead to confusion if users are not aware of the distinction.