I was being clumsy and dropping the plug in the previous pre-filter sponges (also bought from aquarium coop) so many times that I thought it might be better to try something with one side closed off as opposed to another small plastic piece. Highly recommend this for fellow clumsy folks. One less thing to drop and worry :)
I bought 2 of the medium pre filters. One for the intake of my Sunsun 704b canister filter and one for my marineland penguin 100 HOB filter. They fit perfectly with no modifications needed at all. I highly recommend the pre filters.
Still a great product.