The 7V Extension is an optional accessory for use with the 7V heated clothing. Once connected, the 3.5’ cord provides more options for 7V battery placement. This is a useful accessory to pair with the balaclava, any mid layer, or when you just need a little extra cord length.3.5' lengthThe extension is compatible with other heated clothing brands that use the common 3.5 x 1.35mm plug