I looked at these cylindrical filters and nearly bought one when I got my K&N, as I thought they would flow more air due to greater surface area, but ended up going for a cone after a bit of reading and realising the restrictions there would be on space regarding a 6" filter lol. This extract explains best what I came to understand about filter shape if it helps anyone......
"Assuming both filters have the same surface area and same filter media, the cone will outflow the cylinder. The reason for this is because the air coming through the cone flows through straighter wheras the air coming into the cylinder shaped filter has to make a sharp 90 degree bend.
This causes several problems. First, most of the air tends to come in the closest to where the air intake tube is clamped to the filter. Little or no air comes in at the opposite end. This effectively reduces the usable surface area of the cylinder filter (hence: why the more expensive filters are cone shaped). Second, the 90 degree bend the incoming air has to make after passing through the filter media of the cylinder causes the air to hug tight to the intake tube wall. This creates uneven air flow/turbulance. This also increases friction which reduces air flow. The slower air in the middle of the intake tube and the faster air closer to the wall of the tube induce turbulence which further reduces air flow.
The cone filter all but eliminates the sharp transition the air has to make after passing through the filter media. This allows for near 100% air volume through the air intake tube with little or no turbulance. All of the cone filter has equal air velocity/volume passing through it from end to end due to the tapered shape.
In other words, a cone filter with 90 square inches of filter surface will outflow a cylinder filter with 110 square inches of filter media. These surface area numbers are from a 6"diameter by 6" long cylinder (110 square inches) and a 6"lg by 6" base diamer cone (90 square inches)."