Superb Wrench #2 -Galvanized Steel Water Filter Wrench Has 4 ridges with 6.28" diameter fits Big Blue Hydronix housing Fits the following housing : 3M-Cuno-Aqua Pure AP800, AP801 / AP-801, AP801-C / AP801C, AP801-T / AP801T, AP801T-C / AP801TC, AP801-1.5 / AP-801-1.5, AP801-1.5-C / AP801-1.5C, AP801T-1.5 / AP801-T-1.5, AP802 / AP-802, AP802-1.5-C / AP802 1.5C Made of heavy duty 7 gauge steel that will not break, bend or strip the water filter housing unit Lifetime Guarantee! Please email seller if you are not sure of exact size of wrench before placing order to avoid returns.