The Katadyn Combi has a silver impregnated ceramic filter that is filled with activated carbon. Yes, it is refillable. The filter is good for up to 13,000 gallons. The carbon will need to be replace (or simply removed) at about 105 gallons of use.
The filter is 0.2 microns and can be cleaned so that you get more use out of it. It weighs 21 oz (580 grams).