The Apollo 39213-015 is a Dust Cap / Cover for use with the Apollo range of detectors. These are ideal to help prevent dust contamination of detectors during periods such as when building works are taking place.
The Apollo 39213-015 Dust Covers are compatible with the following Apollo Detector ranges:-
Apollo XP95 Detector Range
Apollo Discovery Detector Range
Apollo Series 65 Detector Range
Apollo Alarmsense Detector Range