If you wish to apply more than 4 pads you can purchase extension leads. For the price of $20 you can purchase a set of 4 dual extension leads so you can place 4 pads on each knee.
You can use 8, 16, 32 pads using the extension leads, just depends on how many you wish to buy.
When you buy a set of (4) extension leads you get (4 leads) 2 black and 2 red, this will give you 8 connectors to put 8 single pads on, most tens machines have 2 channels that allow you to connect 2 electrodes to each channel. People who have many sore spots including hip, knee, elbow, lower back can now use the extenders and treat two or four spots at the same time.
Do not use with Apnea Monitors or AC Power Source