Injin cika capsule kayan aiki ne masu mahimmanci a cikin masana'antar magunguna. Suna cika daidai gwargwado mai ƙarfi tare da foda, granules, pellets, da sauran kayan ta hanyar sarrafa tsarin ciyarwa, rabuwa, allurai, rufewa, da fitarwa. Nau'in inji daban-daban suna amfani da ka'idodin cika daban-daban, don haka fahimtar yadda suke aiki yana taimaka wa masana'antun su zaɓi kayan aikin da suka dace don sikelin samarwa, halayen samfur, da kwanciyar hankali.