A filter cartridge 12 that includes a sorbent filter material 42, an end-of-service-life (ESLI) indicator 40, a housing, and a housing cover 24. The housing 22 has a sidewall 26 that has a window pane that allows the ESLI 40 to be viewed through it. The cover 24 is secured to a first perimeter 28 of the housing sidewall 26 and has an air throughput surface 32 and an opaque extension 36. The opaque extension 36 is positioned on the cover 24 such that the extension is juxtapositioned against an outer surface of the housing sidewall 26. The cover extension 36 also has a window pane located in it so that the ESLI 40 may be viewed through it too. The provision of an opaque extension 36 on the cover 24 and a window 38 in the extension 36 allows the ESLI 40 to be appropriately masked such that the sensor registration position is consistently achieved during manufacture of the filter cartridge 12.
