Guard cartridge for 2.1 and 3.0mm ID Ultra AQ C18 columns. 3/pk. Use with Trident Level 2 (cartridge holder only), or Level 3 (filter + cartridge holder.) USP L1, 100A pore size, 15% carbon load, non-endcapped. pH range 2.5 to 8.0, maximum temperature 80C.