Polyester Ring Panel and Link filters offer a durability of a no-carboard heavy wire frame that makes it excel in very wet conditions. This duarability makes them an ideal way to increase the particle removal efficiency/MERV of applications that typically use metal filters - like Make Up Air Units, Pool Units, and Dehumidifing Units. The drawback is this style of filter has traditionally been very restrictive to airflow - but not any more!
Metal air filters have been the standard to provide minimum level of filtration so that the air intakes do not suck in leaves, cottonwood, and other large particulates. The build quality of these filters varies quite a bit with some falling apart within the first couple washes and other last several years. No matter what there is still the maintenace headache of having to wash these filters off and in Northern climates (like ours here in Minnesota/Wisconsin/Dakotas) metal filters have a tendancy to ice-up in winter.
In most frame systems the excess media of ring panel filters acts as a self-sealing mechinism forcing air to pass through the filter media even if the frame system is a little run-down or compared to cheap cardboard frame filters that collapse when they get wet or if they are left in a week or two too long.
Airflow restriction however is the main reason facility engineers have stayed away from ring panel and link filters. With an average inital static pressure of 0.45" w.c. they are the most airflow restrictive (meaning highest energy consuming) option for medium efficiency (MERV 8 - MERV 10) filters. However, one of the biggest manufacturers of ring panel filters, Columbus Industries, has developed a new process for making the media of these filters that gives it a much lower static pressure that is on-par with its pleated counterparts.
This means that you can now get the durability of a ring panel with the static pressure of less than .30" w.c. giving it the energy consumption of a pleated filter!