If you already own a Thermalution Yellow+, then you can purchase an upgrade set, which simply connects to your existing suit, via supplied Y-piece connector.
Available in 4 sizes: Small, Medium, Large & Extra large
No batteries are included in this set.
PLEASE check you existing batteries are suitable to work two Thermalution products by
(1) is the battery marked with a V.2
(2) does the battery code start with a reference P0802 or lower
If yes to either of these items, then your existing batteries are suitable for use with two Thermalution Products
If NOT then you require the Add-on Set with an upgrade of your batteries
(4.4v for Yellow+ & 2.2v for wired series)
(PSD-11-BC ADD-ON System)