filter cap

side cap; garrison / flight cap (US); wedge cap (Canada); field service cap (UK)

band-pass filter / bandpass filter (BPF)

dust filter / dust shield, particle filter

dust shield / dust filter, particle filter

filter housing / filter unit

filter unit / filter housing

particle filter / dust shield, dust filter

finite impulse response filter (FIR-filter)

passband filter; bandpass filter (BPF)

air filter

base cap

cap adapter

cap well (mine, IED)

capability catalogue (CAP CAT)

cap-comforter

combat air patrol (CAP) aircraft

detonating cap

dust cap

field cap

fighter cap/ umbrella

filter-separator

forage cap

fuel filter

fuse cap

garrison cap

gas-particular filter unit (GPFU)

home-made face filter

individual portable filter

locking cap

oil filter

percussion cap

RF interference filter