2 count of replacement filters that fit all Brita Hard Sided Bottles and Brita Sport Bottles;1 water filter can replace 300 standard 16.9 ounce water bottles;Filter sits inside water bottle, reducing particulates and chlorine taste and odor, often found in tap water;For best performance change filter every 40 gallons or 2 months;BPA-free replacement water filters require no pre-soaking