I bought 2 of them from ebay, since none of the local fish shop carry this product. They do have similar product from ISTA but very expensive $27. It cost me S$8.60 for 2 but the delivery charges is S$11.90 which is more expensive than the product. The stamp duty on the mail is only HK$19.1 or S$3.75. Nevertheless, it is still cheaper than ISTA.
I like this product. For starter, it does not reduce the filter flow. Furthermore, I not need to worry about green spot algae. Probably because it is inside cabinet thus no light. However, after a while I can see some brown thing build up (diatome?). It is the same build up that normally hapen inside filter hose. Nothing to be worry about just use brush and clean it during regular filter maintenace. It is much easier to clean compare to green spot algae.