Answer
There are 3 lens variants for ceiling occupancy/vacancy sensors (and applies to both dual tech and non-dual tech). They use very-similar hardware, except the lens installed in the sensor is different. The difference can only be seen from the underside of the lens. See below for images and descriptions.
Note: for safety, the High Ceiling lenses are glued in place in the sensor, so it is not possible to replace them in the field. The Small Room and Large Room sensors' lenses are held in place by pressure from the enclosure and the lens support.
High Ceiling
Large Room/2000 sq ft coverage
- Series of linear striations, may be difficult to see visually but can feel very easily
Small Room/500 sq ft coverage
- Combination of both above, with series of circles with rippling striations