These standard 10 x 2.5 inch sediment cartridges measure about 2.4 x 9.9 inches. This page carries spun, string-wound and melt-blown options from Pentek, Tier1, USWF, American Plumber, 3M Aqua-Pure, Watts Flo-Pro and Purtrex, in micron ratings from 1 to 50.
A 10 x 2.5 filter is a nominal size. The actual cartridge measures about 2.38 x 9.88 inches, as with the Pentek P1 and P5. It fits standard 10-inch housings, so match the size printed on your current cartridge.
A 1 micron cartridge captures the finest particles, 5 micron captures fine silt, and 20 micron captures coarser sediment. Lower-micron cartridges load faster, so choose the highest micron rating that still handles your sediment.
Sediment filter life depends on the cartridge and your water. Culligan rates its P5 at about 2 months or 8,000 gallons. For other cartridges, check the manufacturer's guidance on the product page.
The difference between a 10 x 2.5 and a 10 x 4.5 cartridge is diameter: about 2.4 inches versus 4.5 inches. They fit different housings, standard and Big Blue, so they are not interchangeable.