Review on Fluval Foam Filter Block Replacement: Filter Media for 404, 405, 406, and 407 Aquarium Filters by Melissa Jones

I don't know why the 306 model isn't listed in the name = very misleading and I was apprehensive about ordering at first but I found the same product at a pet store with the same box as this one in the picture but this box had a few other model numbers besides the ones shown here = I took a chance and ordered it (plus it was cheaper here) and lo and behold it's the right size for my 306, I hope this helps anyone who has doubts due to an incomplete description of the product, not the name.