I have a Topfin 10 gallon setup with a HOB from PetSmart. This fits the intake perfectly once I took off the intake guard. It helps keep the main filter cleaner longer which is large sponge coarse pad that I bought at the same time. It also holds any excess food that the fish can then still eat and it also prevents any fry from getting sucked up. Fast shipping and definitely worth the money. I'm sure I'm just one of many after watching Cory's video on YouTube about got hot rodding your filters.
It works well on the intake of a filter, keeping your main filter cleaner longer and preventing any small fish from getting sucked up into the filter. You may have to use a bit of tubing to get it to fit okay.
it fits pretty loosely on my aquaclear50. It falls off during water changes if I bump it