My current cartridges are going on 4yrs now. I was thinking of picking up a spare set to have on hand. Anyway I came across these: 4 Pack Pool Filters Fit C 7483 Hayward SwimClear C3025 CX580XRE Antimicrobial | eBay These cartridges have something called a microban coating or treatment. Are these of any value,harm or just a gimmick?