These are specifically designed for AR-15. Due to variances between manufactures these will most likely not work in an AR platform 308 build.
Yankee Hill Machine does not provide specific dimensions for their EZ Pull Takedown Pins. I would recommend reaching out to them directly for clarification. You can find their contact information linked below:
https://yhm.net/support/
This will be made of steel. As per the manufacturer:
Heat treated and plated to Mil. Specs.
Yes, this will fit most lowers.
No, this is just the pins themselves.
That gun looks to use a proprietary pin system, it may not have the springs and detents that would be necessary to secure these pins. We recommend contacting Walther, they should be able to confirm compatibility.