This is the genuine replacement lamp for the Trojan A model systems. A word about TrojanUVMax™ (Models A through J) The TrojanUVMax™ product line offers models with a wide range of features and benefits, allowing you to select just what you need for each given application. Models A, B4, C4, D4, E4 and F4 are famous for their unique lamp and sleeve assembly that allows for both to be removed in seconds and without any tools! Models G, H & J offer high flow rates and an extremely compact footprint. Additionally, being built on our state-of-the-art Pro Series platform allows them to share in many of the same product advances.