This is a special UVC bulb designed for Laguna filters that fits the Laguna Pressure-Flo 12000. This bulb is particularly unique as it is both single-ended and single-tubed, with all 4 pins on one end. It is suitable for the following filters: Laguna Pressure Flo 14000 Laguna Pressure Flo 28000 * If your model was made pre-2015 you need an official Laguna 25w bulb, however a regular 24w bulb is sufficient for any models made 2015 onwards. ** If your model was made pre-2015 you need 2 x official Laguna 25w bulbs, however 2 x regular 24w bulbs are sufficient for any models made 2015 onwards.