Aquiferco Faucet Mount Water Filters Refill 3 Pack (Replaces PUR Model Numbers RF-3375 and RF-9999) Fits in any PUR Faucet Mount Systems such as FM-3700 3 AquiferCo's Activated Carbon Block Water Filter Replaces PUR RF-9999 and RF-3375 Provides up to 600 gallons of crystal clean water (200 gallons per filter). Enjoy a year and a half of clean, great-tasting drinking water straight from your own faucet.