1. Measure the outside diameter of the cartridge (in inches, +/- 1/32").

2.Measure the cartridge length (in inches, +/- 1/16) including end caps but excluding any handles or other extensions. We recommend measuring through the center (if possible) rather than along the outside edge.

3.Identify the cartridge outside edge end cap configuration using the photograph chart below. If the top and/or bottom is "open," measure the inside diameter (in inches, +/- 1/32) of the top and/or bottom.

4. Record the OEM name and model of the filter the cartridge came out of (if possible).

5. Count the number of pleats (+/- 2), and note whether there is a center core or not.

The information gathered in 1-5 above can then be used to identify a proper replacement. Unicel cartridges are grouped into series based on the approximate outer diameter (O.D.) of the cartridge. For example, the 2000 Series is comprised of cartridges between 2 and 2.99 inches in outer diameter;