Alpine Pure 422mm 40 watt High Output lamp with 4 standard pins Suits all AP PV18T or AP18 UV units. 2 x 20 inch x 4 1/2 inch Alpine Pure Gradient Density prefilters plus the third Granulated Activated Carbon final cartridge. The 20 micron cartridge is first followed by the 1 micron second and the GAC is third. When doing the yearly service please remember to remove and clean the Quartz tube to enable the UV lamp to penetrate through the Quartz Tube to sterilize to water. To reset the ballast, replace the lamp and turn the power supply on, press the reset button on the ballast front face and hold up to 1 minute until the number 365 is showing on the LED readout.