LSE Lighting compatible UV Bulb for use with R3500X and R4000GX Brand: LSE Lighting - Length: 10 1/2" Bulb Type: J Type (U Shape) - Ultraviolet Germicidal UV - Base Type: 4pin Lamp Shape: J Type T6 Dual High Intensity This UV replacement lamp by (LSE Lighting) brand is 100% compatible for use with Purifier models R3500X and R4000GX. All lamps listed are compatible brand (LSE Lighting) brand UV products.