Captain O-Ring – Replacement Seal Oring for SunSun HW304A, HW304B Canister Filter (2 Pack)

I am so glad I was able to use these for my Polar Aurora 4-Stage External Canister Filter 525GPH. The company has discontinued Polar Aurora Canister Filters so they no longer make replacement parts for them. (Frusting when a company discontinued their product just after the warranty expires). What you can find is what is left over. An aquatics company told me that the SunSun is the same Canister Filter so it's replacement parts will fit. This o-ring fit perfectly and now my Canister is fixed. It wouldn't seal after I cleaned it. Water was dripping out from the side latch. Adding lubricant made it worse. I found out that you need to apply a small amount of a food grade lubricant on the o-ring everytime you open and close it to prevent the o-ring from cracking. I bought more incase of a future need.

This returned my leaky Sun Sun canister filter from being a "paperweight" taking up space in my cabinet to being a really good and effective canister filter once again. I plan to do a gasket replacement once a year now so I don't run into this problem again. Pleased that I bought this. Should have done it sooner.

as per describe dimension, good quality.

If you have a SunSun 304B these o-rings are not a direct replacement. These o-rings are not as thick and therefore leak right off the rip. Luckily my existing o-rings was still in good enough shape(probably because of o-ring lube) I was able to recover.

Okay, so I'm am not 100% that the O-ring was the issue, but I had the filter for 7?ish years, and then the filter was dissembled for a couple months were it was just sitting open to air. I bought this new set, and installed it with some petroleum jelly. I do think that my leak was from the UV light cover not being fully inserted and locked in the filter head, BUT I am still glad I replaced the O-ring for my piece of mind. The price is very reasonable and you get two of them. If you even suspect that it is the o-ring, or your filter has been running for years without a change, go ahead and buy these. It can't hurt and now you also have a spare. Or just buy them now so if you do have a leak they are on hand. I keep my filter in one of those big bucket tubs that they sell for keeping toys and sports equipment in. I also have a water sensor that screams if it gets wet. I set the senor in the bottom of the tub, and the box with the battery to the side. It has definitely saved me when some leak occurs and the thing goes off at 5 in the morning screaming, with the tub catching everything and saving my floors.

Fit perfectly!

Fit perfectly

I was concerned this would not fit my 304B sunshine filter as it was listed as a 704B part. I had nothing to worry about, after greasing, it was installed easily, and I have had no leaks in the two weeks my filter has been running. I now have extra on hand and a better part replacement schedule.