12 Packs 2 chambers charcoal water filter compatible with Drinkwell pet fountain only. Compatible models are: ORIGINAL, PLATIUM, BIG BOG, MULTI-TIER, INDOOR/OUTDOOR, MINI, EVERFLOW and ZEN. Food grade activated carbon water filter removes bad tastes and odors from water, keeping it fresh; change every 2-4 weeks to maintain water freshness. Nispira branded filters contain 50% more carbon than generic brands for better and longer-lasting filtration. Filter Size: 3.25" x 5.50" x 0.25" ** Does NOT fit brand WHISKEY CITY or any other brands. It's ONLY for the model listed above. Please check the filter measurement and model before making purchase.