The 3M 5566601 Whole House Standard Diameter Replacement Water Filter Drop-In Cartridge is a replacement water filter cartridge for the AP100 Series Housings and Stainless Steel Housings. This cartridge is a whole house standard diameter and is compatible with the AP100 Series Housings and Stainless Steel Housings. The 3M 5566601 Whole House Standard Diameter Replacement Water Filter Drop-In Cartridge is a replacement water filter cartridge that will help to improve the water quality in your home. The 3M 5566601 Whole House Standard Diameter Replacement Water Filter Drop-In Cartridge is a replacement water filter cartridge for the AP100 Series Housings and Stainless Steel Housings. This cartridge is a whole house standard diameter and is compatible with the AP100 Series Housings and Stainless Steel Housings. The 3M 5566601 Whole House Standard Diameter Replacement Water Filter Drop-In Cartridge is a replacement water filter cartridge that will help to improve the water quality in your home.