Little known secret, these also work with other 58mm espresso machines not just Robot!
I'm experimenting with using them on top and/or bottom of the coffee instead of a puck screen.
On the top it does seem to help keep your espresso machine cleaner similar to the stainless steel puck screens, but I don't think it's as effective as the steel discs for ending up with a nice super dry and solid spent puck. It may also help with water distribution but not sure.
The stainless steel puck screen, which similarly goes on top of the coffee after tamping (which I would generally recommend for dryer pucks and keeping your machine cleaner, but) it was rubbing against my shower screen so I decided to try these (could also just lower my coffee dosage or use a larger basket actually). These are another alternative without risk of damaging shower screen, and also without the extra soaking / cleaning the steel discs need.
Also if concerned about oils in espresso (possibly can affect cholesterol?), this should filter those out (used on the bottom of course)!
On my stock basket that has a smaller diameter at the bottom the paper filter doesn't fit as perfectly as it does on the top however, with something like a straight walled VST basket, it fits a bit better on the bottom (if you put it on top it should fit fine on any 58mm basket).
Update: I don't think you want to use a filter that is too large for your basket where it folds over on the edges, that will likely allow for water to find a path and create a channel.
Good Brothers coffee has a variety of sized papers for the bottom of different baskets, and they work really well!
I've learned with a paper filter on the bottom, you can grind finer and get better / higher extractions generally.
These Robot Filters are probably best for the TOP of your coffee, in lieu of a Stainless Steel Puck Screen.
