Guardian Pool Spa Filter Replaces Unicel C-4405 C4405 Rainbow Dsf 50 Prb25Sf Fc-2387 17-2464 -Bottom Opening: 2 - 1/8" -Top Opening: 2 - 1/8" -Outside Diameter: 4 - 15/16" (Also replaces 5") -Length: 6 5/8" (Combined Total - 13 1/4") -REMAY Filter media