The Wattstopper HBL1M is a masked aisleway replacement lens for HB Series high bay occupancy sensors, providing a 30 ft. x 20 ft. coverage pattern at 40 ft. mounting height. The included opaque masking restricts detection to a narrow aisleway zone, preventing false triggers from cross-aisle traffic at the beginning of rack aisles in warehouse environments. Designed as a field-replaceable lens for compatible HB Series sensor heads.