Universal in size as in 10" nominal lengthbut vary greatly in filtration ability and how well they protect whatever is downstream which is their sole purpose. In the case of a sediment filter it is to protect the billions of tiny microscopic pores in the carbon block where chlorine and organics are adsorbed. 10 microns nominal rated is about as effective as a screen door compared to 1.0.. 0.5 or 0.2 microns absolute or near absolute rated. Same thing with carbons, they can be anything from granular activated carbon good for around 300 total gallons (60 treated and 240 waste at 4:1 waste ratio) up to 20,000 gallons (4,000 treated and 16,000 waste at 4:1) with a single 0.5 or 0.6 micron extruded carbon block and everything in between. A RO membrane or DI filter are not worth a hill of beans if they are not well protected so shop wisely as every component has a purpose Think of the RO/DI as a complete system from beginnning to end and each piece must do its job well or everything past it fails prematurely and costs you more money than if you had used the quality sediment or carbon to begin with. If a RO/DI is treated like a fine tool it will last a decade or more, if not it may need a new membrane in 12-18 months or less.