Culligan 1 in. Whole House Heavy-Duty Wrench is specially designed to make cartridge s easier by loosening the bottom of housings efficiently. This heavy-duty wrench is compatible with Culligan models WH-HD100-O and WH-HD200-C, ensuring a fit for your whole house water filtration system. To use, simply slide the circular end over the housing until it fits snugly, then unscrew to remove. It is important to note that this wrench should not be used to tighten the bottom of the housing; instead, hand-tighten the bottom onto the cap to avoid cracking. This tool provides reliable performance and durability for maintaining your water filtration system. Model Number: WR-HD