"Works" is a relative term since a buck has to smell it for it to work. What the deer is smelling is mostly the faint aroma from ammonia as the urine breaks down, that piques it's curiosity enough to check out the source. Once it arrives at the source it begins analyzing any other odors such as pheromones, which means it has to be close to the source since they don't carry far before degrading. The smell of another deer works at least as well as urine, and usually better since another deer is either going to be a date or a rival. I've had deer follow my scent trail for hundreds of yards while wearing Deer Dander™, never had that kind of reaction from pee.