Cleaning kit is originally designed with a small grease reservoir, pull through cord and a brush & cleaning patch eyelet. These are just the empty housing and can be used to store a small item like a battery or to close off the grip. These work only with a plastic grip that has the small internal notch, such as RSA, FN, IMBEL, Argy. StG-58 grips do not have. Must also use a small head grip nut.