Juwel Filter Basket System suitable for Rio 300, Rio 400, Delta 300, Trigon 350. Using Juwel filter baskets means that you may assemble your filter sponges outside the aquarium and then slide the complete basket into place in one action. No more fiddling about with your hand submerged at the bottom of the filter.Removal of your used filters is just as easy. Just pull on the top of the basket and the whole assembly just slides out. Just follow the four easy steps shown to maintain your filter system. There are 2 baskets per pack as shown in the picture.