FREE Shipping! UV electric 4-pin solid state transformer for all post-2011 UV units. What is the difference between the pre-2011 2-pin UV transformer and this new post-2011 4-pin UV transformer? Just a slight upgrade in quality and improvement of the new solid state transformer. The new transformer has 4 pins, so the UV lamp now has 4 pins instead of 2 to make the connection. All UV units made in 2011 and after will come standard with the 4-pin UV lamp and transformer. If you have a pre-2011 UV unit, you may upgrade to the 4-pin assembly easily by clicking here. Compatible ONLY with EWS sink filtration and RO systems with UV.