This is the pump for the HydroFloss oral irrigator, one of the best things you can have in your home for your dental health.
The model number of the HydroFloss that this part fits is 7618.034. This number can be found on the bottom of your HydroFloss oral irrigator.
There is actually a handy video that shows you how to replace the pump and that video is available on this HydroFloss pump and piston page.
This is a nice option for people who would rather DIY repair their HydroFloss than pay $98 for a new HydroFloss Oral Irrigator
My general rule of thumb can be taken with a grain of salt - There is absolutely no reason to agree or disagree. Everyone makes their own choice.
That rule of thumb is when the HydroFloss is older than 3 years old, get a new one. Under 3 years old, repair if you can.
Again, I am not asking you to follow those guidelines. That is just my personal opinion. I only share it because someone might find it helpful.