BOTTOM LINE
If I could go back, I'd pay a few more dollars for a better pitter with metal parts - something that has a grip and is rated to be used with cherries AND olives.
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IT WORKS ON CHERRIES
First, off, I want to say that the Westmark Cherry Pitter works for cherries, especially if they are softer. If that's all you want or need, then this is perfect.
DOESN'T WORK ON OLIVES
Unless the olives are of the very soft variety, this pitter has a hard time on olives. I imagine that, if a cherry is sufficiently firm, it might also give a little resistant. The pitter is also not big enough to accommodate medium-to-large olives.
POOR ERGONOMICS
For me, the pitter is oddly small, and I have a hard time using it. I don't have big hands by any means - I think the issue is more the lack of grip or the narrow width of the pitter. The pitter slips out of my hands easily during use, and, when I am pitting olives, the pitter has a tendency to snap shut and pinch my hand or fingers.
POOR BUILD QUALITY - PLASTIC!
The Westmark Cherry Pitter is made of plastic. I didn't realize that initially when I bought it, but I can tell now by inspecting the picture. There are nicer pitters out there, with metal parts, for only a bit more. The problem with plastic is that the parts don't have weight behind them and don't move smoothly. I haven't broken mine, but I could imagine that this pitter is less durable than I'd like.