24x30x1-merv 12 A/c Furnace Air Filters By Nordic Pure

These MERV 12 filters are a nice step up from the fiber filters you get in the local hardware store. They felt-like pleat really capture the dirt.

This is a huge filter, so it's hard for a piece of cardboard to remain rigid. During the summer when the humidity is higher, I've had the filter get sucked into my air handler, though I honestly think that the fault of my filter port there's no cross beam to provide support for the center of the filter. However, keep this in mind if you're buying a large filter like this.

Not much more to say the filters do their job and you throw them away every month or two. It's not a sexy part of your HVAC system, but it's an essential one.