I have a 4-way switch configured as this diagram: https://community.smartthings.com/uploads/short-url/2XsNgufHV32z5d65v8UVVGw38jO.png
Will the lutron caseta dimmer work? which switch should it replace? and what happens to the wires in t he other switches?
With the regular dimmer (not 3way), you’d have to replace two of the switches with pico remotes and adapter plates.
EDITED:
With the pro dimmer (3way), you need a neutral, so not an option.
That’s great except he doesn’t have a neutral which is why he asked about caseta. 
In the diagram, it shows a black and white from panel going to the light first. That means the two wires going to the first switch are a constant power and switched power: no neutral. In residential, a white wire at a switch can be a neutral, carry constant power, or be a traveller wire between 3 and 4way switches. In this configuration the only way to use a switch that requires a neutral is to replace the 2 conductor wire from the switch to light with a 3 conductor wire.
Crap. I double checked the wiring requirements for the pro dimmer and a neutral is required. Edited original reply.
