I thought these filters didnt fit and I was so upset, I couldnt make a seal and the filter housing was leaking. I was about to return them. When I removed the big blue housing and fiddled with the filter, it fell into the circular slot and boom it fit afterwards. Very happy now and almost returned these by accident. This filter is 10 inches long and the one I used before was 9.6 inches. I actually think the 10 inch filter is the correct size, since it is a tighter fit top to bottom, it takes a little fiddling, but probably are the correct manufacturer specifications. The smaller filter was easier, too easy and might not have actually been working optimally.