Fresnel lens are available in .65 or .90.

You can choose the .65 fresnel lens which will allow for detection at distances up to 90 feet or the .90 fresnel lens which will detect out to about 60 feet but has a wider detection zone. The detection zone for the .65 is about 3 feet at 25 feet where the .90 will have a detection zone of 15 to 18 feet wide at that distance.