I tend to buy bigger than needed as it is simple and easy to cut flow down while very difficult to impossible to get more without rebuying. Flow on this is close to too high and many might want smaller but I do find I tend to get larger tanks and flow does cut down as the media gets dirty, so "too big" is okay for me and this is one that sells for 40-75 depending on what media is included. Flow tends to varty a whole bunch, both in how much I want and how much it works in different tanks with different plants and decor. Open tanks with small plants don't block flow and it can shoot all the way across but when I get things stuffed with plants, rocks and wood, things slow down a bunch. When I find too much, I stick a sponge on the intake to slow it down. Sunsun does use a thinner plastic but then I find I work careful and don't break very much and then if I do the parts are so much cheaper that I feel I can replace something if/ when I do break it.