We have Watts WQCFU-T-11 3 Stage Kwik Change Ultrafiltration Replacement Filters. This is a yearly filter pack and it includes:
2 - WQCSC11 11" Sediment PreFilter (Red)
2 - WQCCC11 11" Carbon Block Prefilter (yellow)
1 - WQCHFC11 11" Hollow Fiber Ultrafiltration Membrane (Purple)
The Sediment Filter and Carbon filter needs to be changed every 6 months while the membrane needs to be replaced annually. Everything you need to keep your system working optimally for a full year.