Red SeaReefer Filter Media Cup - 4" Durable Aquarium Filter Sock Replacement - Easy Maintenance for Saltwater & Reef Tanks

I'm using these cups in my Reefer 750 XXL so when I bought my new 425 XL it came with 2 cups and 2 socks....I can't stand the socks so I bought 2 of these cupsProsI just load the cups with floss, media, etc... and I'm good to go, no more pulling slimy, dirty filter socks and having to clean themThey're solid and thick and have large flow slots, especially compared to some after market cups I've used that didn't have the same water flow through themThey fit very well in my sock holders, no issue with them sliding in and out easilyThey save so much time for my tank maintenance, I just pull out the dirty floss, throw it in the trash and replace with new floss....doneConsThe only downside to these cups are the price, but you have to figure out how much time you save each week using them and how easy filter media changes are and you won't mind paying a few bucks for them.

A little pricey but well worth the money

This is a very solid built filter cup, almost no play in it even if squeezed hard. That shows quality plastic was used but might be an issue if you need to squeeze it smaller to fit through a sump's filter sock opening. But if you have the space for it to fit this should last forever.

Highly recommend!

Absolutely love having this! I fill it up with floss and its ten times better then changing out filter socks! Fits in my 4 inch sock holder perfectly!

Had a hard time for years finding filter socks that fit my Prostar 150 sump as the openings are less than 4”. More like 3.75”. These Red Sea filter cups drop right in and I can easily just stuff with filter floss which I buy cheap in 6’ rolls and dispose of every 5 days or so. Much easier and no hassle with trying to cram normal 4” filter socks into that smaller opening.

I drop a bag of carbon or gfo in. It does its job.

Nice cup fits my slot in the sump. I fill it with craft fill much cheaper and does a good job