 They also can be replaced without replacing the entire upper receptacle, and larger receptacles can simply use more filter candles, permitting filter manufacture to be standardized.If a filter in a multifilter receptacle is found to be broken, the filter hole can be plugged, and use can continue with fewer filters and a longer refill-time until a replacement can be obtained.Also, standardizing the filter makes it economical to keep one or a few filters on hand.