This is the 3rd time I have ordered these filters for my Pelican prefilter and water conditioning system (charcoal and Naturesoft canisters). They fit perfectly and come with replacement o-rings and silicone grease for a simple changeout. I know they works as intended because of the rusty color of the one I changed out. Insignificant change in water pressure. For me, they definitely need changing after 5-6 months.
Will order again.