Case size for iPad Pro 12.9 4th Generation (A1584)

4th gen tech specs

Size and Weight2

• Wi-Fi models
  • Width: 8.46 inches (214.9 mm)
  • Height: 11.04 inches (280.6 mm)
  • Depth: 0.23 inch (5.9 mm)
  • Weight: 1.41 pounds (641 grams)
• Wi-Fi + Cellular models
  • Width: 8.46 inches (214.9 mm)
  • Height: 11.04 inches (280.6 mm)
  • Depth: 0.23 inch (5.9 mm)
  • Weight: 1.42 pounds (643 grams)

https://support.apple.com/kb/SP815

Third gen tech specs

Size and Weight2

• Wi-Fi models
  • Width: 8.46 inches (214.9 mm)
  • Height: 11.04 inches (280.6 mm)
  • Depth: 0.23 inch (5.9 mm)
  • Weight: 1.39 pounds (631 grams)
• Wi-Fi + Cellular models
  • Width: 8.46 inches (214.9 mm)
  • Height: 11.04 inches (280.6 mm)
  • Depth: 0.23 inch (5.9 mm)
  • Weight: 1.4 pounds (633 grams)

https://support.apple.com/kb/SP785

So make sure the ports are all in the same place but measurement wise they look the same

A case designed for a 4th Generation iPad Pro should fit a 3rd Generation iPad Pro of the same size. However, the reverse is perhaps unlikely.

The 4th Generation iPad Pro has a large square camera array “bump” one the rear side of the iPad - which a case must accommodate. The 3rd Generation iPad Pro has a much smaller circular “bump” for its single camera. As such, the smaller bump will fit within the larger aperture required for a 4th Generation iPad.

Reputable mainstream case brands will list the iPad models for which they are compatible.