found at DigiDirect
Built as a replacement phone mount for their carbon and aluminum Travel Tripod models, the Peak Design Travel Tripod Phone Mount is a universal phone mount that fits phones up to 3.54 wide, including the iPhone 11 Pro Max. When not in use, this mount hides away in the Travel Tripod's center column for easy accessibility. Pull and twist the G-hook at the bottom to release or stow, and it's held inside by a magnet so it won't fall out. The lightweight tripod and phone mount combo may also be used as a selfie stock.
Note: The Travel Tripod is sold separately.