Names the capacity it will not fit, and brings brushes
OPISICEN OP-00003, 34-piece set
A 34-piece set for 2 L, 2.8 L and 4 L fountains, stating plainly that it does not fit 84 oz / 2.5 L, with two pump brushes included.
What you are getting
Sixteen carbon filters, sixteen sponges and two cleaning brushes — 34 pieces for $19.99, or $1.25 a filter.
It publishes the exclusion the rest of the shelf needs
“ONLY Compatible with 95 oz / 2.8 L & 67 oz / 2 L & 135 oz / 4 L Pet Fountain. Note, Not compatible with 84 oz / 2.5 L.”
One sentence, and it settles the question that splits this shelf. The Cirfifth set here is for 84 oz / 2.5 L and nothing else; this one is for everything except. Between the two, a buyer can tell which pack is theirs without guessing.
The same part as two other brands
Filter 3.9 × 3.9 × 0.4 inch, sponge 1.5 × 1.1 × 1.0 inch — identical to the VANVE and Porens sets on this shelf, to the tenth of an inch. Three brands, one generic filter, three prices: $1.06, $1.25 and $1.33 per filter.
What this one adds for the difference is two brushes.
Two brushes, two sizes
“2 different sizes CLEANING BRUSH… whether it’s all corners of the fountain or water pipelines”. The narrow one is for the pump channel, which is where the slime that kills flow actually sits — and which no filter reaches.
That is a real addition on a shelf where the fountain’s own plumbing is the usual failure point.
What it claims, and what it can show
The health argument — “reduce the risk of urinary tract infections” — is the maker’s, not a measurement. What is checkable is the three-layer construction and the dimensions, and both are published.
What is not published
No carbon weight, no flow rate, and no life beyond the two-to-four-week interval.
Availability
Read on the day this page was built: $20 at the American Amazon shop.
Read from Keepa on the day this page was last revised; stock and price both move without notice.
Prices quoted in this text were read on 2026-10-06. The live price is at the top of the page.
The questions owners ask
What makes it different from the VANVE set?
Two brushes, and nineteen cents a filter. The filters themselves publish identical dimensions — 3.9 × 3.9 × 0.4 inch, with a 1.5 × 1.1 × 1.0 inch sponge — as do the Porens filters on this shelf. Three brands are selling the same generic part. What OPISICEN adds is a cleaning brush in two sizes, and the narrow one reaches the pump channel that no filter touches.
Is 84 oz really excluded?
Yes, and it is written on the listing: "Note, Not compatible with 84 oz / 2.5 L". That is unusually useful, because 2.5 L fountains are common and the filter looks similar. The Cirfifth set on this shelf is the one made for that capacity — and it in turn excludes Catit, which also builds at 2.5 L.
Does a filter reduce urinary infections?
The listing argues that cleaner, better-tasting water increases how much a cat drinks, and that more drinking lowers the risk. The first half is plausible and the second is a veterinary claim the page does not support with anything. What can be checked here is construction: three layers, named, and a filter dimension you can measure.
