Review (3/5): Works as described.  Use taller 3 oz cups with pump.
Bought the pump for my elderly mother-in-law who has difficulty lifting the larger size mouthwash bottles and opening the caps. Works fine for our needs.
Pros:
Fits Listerine Zero 1.5L bottles. Can't comment on whether it fits other brands or sizes but based on previous reviews, sounds like it doesn't fit other brands.
Makes it easier to dispense product vs. lifting and pouring out product.
Inexpensive solution - I paid $6.50 with free Prime shipping.
Cons:
Pump dispenses additional product as it releases/comes back up so be prepared for this and keep your cup beneath the spout the entire time until it has reset to the starting position.
Spout tip is angled outwards so place your cup directly underneath the tip to keep product in cup.
Pump flow is strong so definitely use a taller larger cup or you'll get splash back. I'd recommend the standard 3 oz Dixie type cups. I bought the tiny 3/4 oz paper medicine type cups thinking that would work but they're a tad too difficult to use with the pump.